I've read about this before, actually... I don't remember the exact wording, but it was something like that the patriarchy requires everything that a man does to hold authority over a woman, so penetration is perceived and understood as a form of domination over the one who is penetrated. The woman --- read: the one who is penetrated, as in patriarchy a man cannot be penetrated --- has no agency in sex, so if you're being penetrated you are not "having sex," you are "being fucked" by someone else.
As is mentioned in the post, PieFed has Feeds. They're really cool! There's also the topics system, which is great if you want to browse specific categories without necessarily focusing on any one given community.
one of the greatest memes of all time