First you have to separate the action from the guilt - they are separate.  In the natural law, most actions are neutral acts (i.e. neither morally good nor evil) until circuмstances or intent enters the equation and then a sin is committed.

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Yes, of course.
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But when we talk about acts related to God and religion, ANY offense against these areas are ALWAYS wrong, independent of intent or circuмstances.  This is because offenses directly against God are inherently evil, since God is all-holy.  There are no morally neutral acts towards God - all acts contrary to holiness are wrong, in and of themselves because Holiness exists outside of ourselves.  The intent/circuмstances affects our guilt, but the act against God is still wrong.

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Example:  A 3 yr old goes around saying blasphemy and horrible things about God.  What he said is gravely offensive but he's not guilty because he doesn't know better.

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In other words, it isn't a sin.  Classes of actions or events that we might call "natural evils," "objective evils", or whatever other adjective to describe the matter of an action which is grave do not fall into the category of sin just because they are grave.

No, it's still a sin you're just not guilty for it.  If a protestant during the protestant revolt descecrated a tabernacle filled with hosts, is God not offended?  If a hindu blasphemes Our Lady's virginity is she still not offended?  Of course.  The offense against God is SEPARATE from the guilt.  
If you're speaking of natural evils, I agree with you.  I disagree when we're talking about evils against God/religion.

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I totally reject the idea that someone can commit a sin without imputation of guilt.  The onus is on you to justify such an idea, and with more than just your intuition. 

Don't you two need to be making a distinction between formal and material sin?  Material sin is an objectively sinful act.  But the imputation of guilt belongs to formal sin. This is the moral culpability that is affected by subjective factors of will and knowledge.

I think that you are talking about formal sin while Pax means to talk about material sin, but is confused about the imputation of guilt.

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It's not a distinction that will help him, since material sin isn't sin anymore than a "material chair" (a tree or a pile of wood) could sensibly be called a chair.
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Don't know if saying material sin=an objectively sinful act is correct either.  Depending on what one means by objective; objective is often used in these contexts to describe what really is, despite whatever disagreement or confusion there may be.  Well, if something isn't really sin (as is the case with material sin), then it isn't objectively sinful either.

A material sin is an action which would be sinful in the proper sense (formally sinful, or actually sinful, or however one wishes to phrase it-- i.e., a sin which imputes guilt) if it were committed with knowledge, will, and intent.  It doesn't necessarily have to be something dramatic or "intrinsically evil"; for a Catholic, eating meat on Friday because you innocently thought it was Thursday would be a material sin, which is to say not a sin at all (this is an example from McHugh and Callan).
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Is this the sense of what you're trying to say, Pax?  If so, there is still a gap to bridge between this and the idea that God is offended by material sin.  Which is the point I'm objecting to.

Don't you two need to be making a distinction between formal and material sin?  Material sin is an objectively sinful act.  But the imputation of guilt belongs to formal sin. This is the moral culpability that is affected by subjective factors of will and knowledge.

I think that you are talking about formal sin while Pax means to talk about material sin, but I'm not sure what he is saying about the imputation of guilt.

Yes, this is what we're debating.  The objective/material evil exists outside of sin, because the offense to God exists outside of the sinner, since God's laws exist outside of man.  Some acts are only immoral because of their intent.  Some acts are immoral even when the intent is confused or ignorance exists.

As St Thomas said:  To sin against God is common to all sins, in so far as the order to God includes every human order; but in so far as order to God surpasses the other two orders, sin against God is a special kind of sin.  (Question 72, article 4)

Example 1:  Eating a cookie is not an immoral act.  But it becomes immoral if you eat one in disobedience to your mother.
Objectively, eating a cookie is a morally neutral act.  It becomes wrong only because of circuмstances and intent (circuмstance of the mother's order and the intent of the child to disobey).

Example 2:  A 3 yr old child uses blasphemy.  This is an objectively evil act because blashemy offends God.  But the child is not guilty for the sin due to ignorance.
Objectively, the act of blasphemy can never be neutral; it is always wrong because it always offends God.  But circuмstances and intent can mean that even if the act is evil, a sin is not committed.
As St Thomas said:  If the ignorance be such as to excuse sin altogether, as the ignorance of a madman or an imbecile, then he that commits fornication in a state of such ignorance, commits no sin either mortal or venial. (Question 88, article 6)

Example 3:  A non-catholic couple who uses contraception commits a grave sin, even if they are "ignorant".  This is because sins against the natural law are written on every man's heart and such sins are intrinsically evil.  Objectively, they committed evil.  Was their act sinful, in the sense that they were aware of its sinfulness?  God will have to judge their hearts, but ignorance of the law is also a sin.

As St Thomas said:  But if the ignorance be not invincible, then the ignorance itself is a sin, and contains within itself the lack of the love of God, in so far as a man neglects to learn those things whereby he can safeguard himself in the love of God. (Question 88, article 6)

But I would not call every material/objective evil a sin.  I would call those evils.

Agree.  It depends on the situation.

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In the case of the new mass, we have many different scenarios to think about.
1) the new mass deals with a corruption, scandal and sacrilige of the Holiest of all prayers and of the holiest of all our Catholic sacraments.  Therefore, evils which are contrary to the highest perfection are necessarily evils of the highest degree.

2)  As Augustine says (Contra Mendacium vii), "those things which are evil in themselves, cannot be well done for any good end."  This applies to evils contrary to religion and God, because a corruption of perfection in the order of religion is inherently evil and can never be good.

3)  As St Thomas says above, ignorance can exuse one from sin (to a degree), but ignorance itself is a sin, so that one who commits sins in ignorance is guilty just as one is guilty of the sins they commit while drunk.  Ignorace is a sin of omission by not informing your conscience of its duties towards God.  Drunkenness is the active hindering of one's reason and conscience (i.e. a temporary ignorance).

I totally reject the idea that someone can commit a sin without imputation of guilt.

St Augustine says that: "Sin is a desire contrary to the eternal law."  St Thomas, in Q71, article 6 says:
The first cause of sin is in the will, which commands all voluntary acts, in which alone is sin to be found: and hence it is that Augustine sometimes defines sin in reference to the will alone. But since external acts also pertain to the substance of sin, through being evil of themselves, as stated, it was necessary in defining sin to include something referring to external action.

Why do we say that Sin is against the eternal law and not against reason?
St Thomas continues:  The theologian considers sin chiefly as an offense against God; and the moral philosopher, as something contrary to reason. Hence Augustine defines sin with reference to its being "contrary to the eternal law," more fittingly than with reference to its being contrary to reason; the more so, as the eternal law directs us in many things that surpass human reason, e.g. in matters of faith.

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Conclusion:
In matters of Faith and of religion, our reason cannot teach itself nor conclude to the truths of God.  Therefore, we must educate ourselves as to what God requires and we have a moral duty to have a well-formed conscience and to know what is necessary to please God and how He wants us to worship Him.  Since we are all born with reason and intelligence and all catholics have been baptized and receive the gift of Faith, if we do not know how to love God, it is our fault.  To worship God in a manner that is not ordained by Him, that is offensive to Him, that is irreverent to Him, is an evil in and of itself because all acts contrary to God, the all-good, are evil.  Therefore, attendance at the new mass is evil, it is a sin (since it is contrary to the Eternal law) even if (in some cases) the guilt for such sins differs person to person, depending on the level of their willful ignorance and religious sloth.  For God desires all men to be saved and He will instruct the ignorant if He is asked through prayer.