“Spilling the semen is another form of barrier contraception, employed by Onan, but you seem to either not realize that there is no difference between using a condom and the sin of Onan...”
There is a difference.
The story of Onan:
“8 Then Judah said to Onan, “Go in to your brother’s wife and perform the duty of a brother-in-law to her, and raise up offspring for your brother.” 9 But Onan knew that the offspring would not be his. So whenever he went in to his brother’s wife he would waste the semen on the ground, so as not to give offspring to his brother. 10 And what he did was wicked in the sight of the Lord, and he put him to death also.”
Notice Onan was going to his brother’s wife & having sex with her for the express purpose of giving her a child. Onan was willing to go have the sex, but not to have the kid - and the only justification for having sex with his brother’s wife WAS to have children.
This was a time when childbearing was more important than it is now, unless the Catholic Church still teaches that if your brother dies without offspring, you should go sleep with his widow and give her kids...
“Further, if your lovemaking during a fertile period leads you to intercourse that just could not be resisted, — well, so God is leading you to make another baby. Don’t fight God.”
By the same reasoning, do not lock your doors. If God sends the thief, who are you to object?
The question rests on if a man can use his brain to modify the results of what he does. If God sends me a headache, can I use aspirin to ‘thwart’ his will? I just had a mole removed, and the biopsy is cancer...so I’m going back in a couple of weeks to have a bigger hole made, hopefully removing all the cancer God has sent my way. I also use seatbelts when I drive, rather than refuse to drive at all. If God sends a drunk driver into the side of my car, I’d like to modify the likely outcome.
“It can allow the mechanics of the intercourse, but it would no longer be lovemaking. How so?...Sexual love with the procreative possibility removed is two people lying “I love you” with their bodies.”
Indeed...how so? My wife will not get pregnant if if I make love to her tonight, so it is no longer love-making, but something else? It will be a lie, just animalistic rubbing of bodies? Sorry, we think otherwise - and so do the overwhelming majority of men and women. We are humans, not dogs. Sex isn’t just procreation. Intercourse is entirely possible without the female being in heat, or even close to it.
It is written, “Therefore a man shall leave his father and his mother and hold fast to his wife, and they shall become one flesh.” Not, “they create a baby, one flesh”. Oneness without always creating a new one. It is not the way of dogs, but it is the way of man.
What does that remind you of?
the only justification for having sex with his brother’s wife WAS to have children.
The punishment for not fulfilling the levirical marriage was that the widow would publicly spit on the unwilling husband wile tasking his shoe (Deut 25:9). but Onan was punished by death, not for what he failed to do, but "because he did a detestable thing" (Gen 38:10). The only thing he did different from any other married couple was, he spilled his seed. That is what was "detestable" and the reason God killed him, Bible tells us.
The question rests on if a man can use his brain to modify the results of what he does
Generally, yes, provided that which he does is righteous act. Using medical technology for the purpose of healing is good as any healing is good. Using the same for a sinful purpose is not good. So the question is not at all whether to use modern technology for achieving contraception but whether to use contraception.
My wife will not get pregnant if if I make love to her tonight, so it is no longer love-making, but something else?
If it is not contracepted sex it is love making, and a righteous act because that is the act that makes babies, and if it is, then it is not lovemaking, because it is an act that only simulates making babies but in fact ensures none is made, -- a lie ad a sin. Her physiological condition has nothing to do with it. I did not make that clear?