In my (admittedly informal) readings, it seems to me that the Sin of Onan has ALWAYS in Church history been considered to be a sin of lust because he took the woman and withdrew specifically to avoid impregnating her. In this way, he reduced sex to selfish pleasure instead of mutually self giving love. Onanism historically was defined as any such method like withdrawal or condoms (surprise, they aren’t new to history! Used to be sheep intestines…).
I’m pretty sure none of our Orthodox friends here can cite a pre-1800 patriarch or any Early Father defending the use of a condom or withdrawal for the purpose of avoiding conception. If they are honest, they are going to have to admit that it is a recent “insight” to determine that proactively defeating natural fertility can sometimes be OK depending on the situation. Note that NFP has never defeated or frustrated natural fertility. What surprises me the most is that its the catholics who recognized the difference and the crucial factor of a “sexual fast” (the NFP abstinance time) that opens the soul to hear God’s (name removed by moderator)ut on just how “serious” a couples reason for avoiding is. Usually orthodox spirituality is admittedly better at appreciating the value of fasting in hearing God’s voice… Why not this time??
EDIT:
On second thought, most catholics DON’T get it. A couple of popes ‘got it’, upheld the teaching even after the culture changed and it became unpopular and now a growing number of us are recognizing what a genius insight it truly was! THAT’s food for thought…