The implication being that there are SJ people who believe this, and know it sounds awful to everyone else, and then spread it and blame it on 4chan in case it backfires?
Occam's Razor. We know trolls exist. We know that specifically trolls who pretend to have insane SJ positions exist. We know almost no SJ person would ever dare say anything denying a woman's rape*. I can't imagine why "this is what SJ people ACTUALLY BELIEVE" would win as a hypothesis against "troll troll troll troll troll".
Apologies if that is not what you mean.
*A man's rape is a whole other thing entirely, unfortunately...
ETA: Actually, let's make this empirical. Anyone who thinks the poster is legit, can you find me one actual SJ person posting it and agreeing with it? I've looked before and found nothing.