A friend of mine linked me to an article the other day which described how "waiting on God" is an active, rather than a passive process. Because waiting on God should actually translate into "abiding in Christ" (and not merely twiddling one's thumbs.)
Applying this logic, I figured that NFP wasn't sexist because it promotes abstinence within marriage. An 'active' abstinence involving both the man and woman sacrificially forgoing sex for a time for whatever reason (like if either the husband or wife were sick for example.)
Saint Paul advised that there is benefit to be had in taking times of mutual abstinence for prayer and fasting:
5 Do not deprive one another except with consent for a time, that you may give yourselves to fasting and prayer; and come together again so that Satan does not tempt you because of your lack of self-control. 6 But I say this as a concession, not as a commandment. (1 Corinthians 7)
And either way, always leaving the room for the possibility that God will still open one's womb even if 'unplanned' from the earthly end of things.
I agree with you on the concept. Perhaps it just breaks down in our culture, where the assumption is that there is some cosmic injustice going on if a person feels a sexual urge and can’t act on it.
Healthy women’s sexual desires are strongest when they are fertile. (Hello, Darwin, nice to see you ...) When there is a fear of reproduction, this basic fact of biology creates the perception that women’s bodies are bad. God just got it WRONG!