My understanding (always said with the caveat that it is my current [i.e. subject to change] understanding) of sin is that it is at its core an offense against and in the eyes of God. 
Help? I think??

It's common sense.

A lie about a small matter is not the same thing as publicly slandering a man or attempting to destroy his reputation. For example, coming forward and saying that a Supreme Court nominee tried to sɛҳuąƖly assault you 36 years ago, when such isn't the case (or you can't remember who sɛҳuąƖly assaulted you 36 years ago because you were drunk).

And sin is always to be condemned, even if we ourselves sin. Obviously it behooves us to cut our neighbor some slack, especially regarding venial sins which virtually everyone commits. But it would be foolish to let murderers, rapists, traitors, and other serious criminals off the hook, because "we are sinners ourselves!" or "who can cast the first stone?" (perhaps yesterday you got angry while in traffic).

God is MORE just than man, not less just. So if we (being evil and imperfect) can distinguish the difference between stealing a candy bar from a store, and embezzling a widow out of her life savings, don't you think God makes such a distinction as well?

Put aside sin for the moment.

1. A hammer falls on a man's toe. His toenail is bruised and painful.
2. A brick wall falls on a child and she becomes paraplegic.

These things (which are not sins) are both bad.
Is there a degree of badness?

Yes, of course. The results of the first example are temporary and slight.
The results of the second are permanent and serious.

There are different degrees in everything. The same applies to sin.

Nobody is saying degree never takes away from the fact that it’s a wrong action/thought/deed etc. Sin is sin, as you rightly say. But, as Matthew said, It's common sense....don't you think God makes such a distinction as well?