A long tradition in our society holds that being pentrated is feminine and therefore shameful for men.

These ideas go back more than 2,000 years, at least, to the days of ancient Greek and Roman societies that popularized them. It's funny that "Greek" in reference to sexual practices used to be shorthand for anal penetration — reflecting a modern misconception that men of ancient Greece enjoyed being anally penetrated. I'm sure some of them did, but if word got out they faced disastrous social consequences. Being anally penetrated was for slaves and low-status men who did sex work. All other men were expected to do the penetrating.

Even among men who have sex with men in today's world, the shame of being penetrated persists. Even among many men who identify as gay, it persists.

It's all misogyny, of course. It's all down to the idea that men who behave like women are weak and shameful.