CathInfo.com

 There is still a question in my mind:
Pro-NFPs say that this method is only about union this time, no union that time, and as people are free to choose the time, then it is OK.
 But I don't think it is that easy, you know christians can eat everything they want, if you use the above logic, then pills are about eating (or swallowing) so they are ok.

Poisons of sterility are not foods.  They are harmful drugs that alter the physiology of the body.  

 I can reach the conclusion that it is the intent that makes it sinful not the act per se. For example, if a virginal or very very old person is told to use pills for reasons like balancing some hormones or hair growth, then pills can be perhaps OK, as those people have no chance of getting pregnant anyway they can't intent contraception.

I would be very skeptical of any administration of birth control pills for other reasons.  It is a sinister method of promoting birth control.  Advising the use hormone replacement therapy to nearly all post-menopausal (as was once done here) was another way of promoting life-long treatment with birth control hormones.  Birth control pills do not only cause sterility, they affect the psychology of women.

 

The intention is all the same in pills, NFP etc : union for mere pleasure, and avoiding a child intentionally.

Abstaining during the fertile period cannot be a matter of pursuing pleasure.  And there is a right to alleviate concupiscence.  Ideally those who cannot afford children would abstain completely, but human weakness and the right to the marriage debt means that the debt cannot be refused at any time.

 Old couples and barren people aren't avoiding a child intentionally, it is just God's design, not their's, that prevent pregnancy.
  The fact that you are wellcoming a baby who may come inspite of what you do, doesn't justify anything. I know pill user and IUD women, who wellcomed their babies, saying:"God wanted this"

The pill, IUD, condom, mutilate and corrupt the human physiology.  Simple periodic abstinence from sex does not do that.

The intention behind the use of NFP can be evil though.