“All of Christianity, Protestant, Orthodox, and Catholic unanimously taught since the times of the Apostles that contraception was always sinful and that Onan died for it. It is incontrovertible and uncontested that this is a fact.”
When I read the verse for the first time and without council from anyone I gathered God was angry because Onan disobeyed him not because he spilled his seed (subtle distinction). I’m sure it’s been debated over and over and maybe there is additional context in other writings that can confirm or deny which it was that made God angry. It’s worth noting I’m a Protestant not a Catholic.
“But Onan knew that the heir would not be his; and it came to pass, when he went in to his brother’s wife, that he emitted on the ground, lest he should give an heir to his brother. And the thing which he did displeased the LORD; therefore He killed him also.””
Actually, no, prior to 1930 it was never debated, anywhere, in Christian writings. The interpretation of the Onan incident has been unanimously upheld by Protestants, Orthodox, and Catholics until just 4 generations ago.
Therefore anyone who proposes an alternative interpretation has the obligation to disprove the prior unanimous interpretation and prove their own.
Fortunately Deuteronomy 25:5 gives us the key to its proper interpretation, and that was certainly taken into consideration by Protestants, Orthodox, and Catholics until just 4 generations ago.