If I had a nickel for every yaoi I read with a guy getting his dick magically disappear due to his promiscuity, I would have 3 nickels. Which isn't a lot but it's weird it happened thrice.
i cannot say for sure but it might be "boy meets girl" and " do you believe humans can be evil" or smth like that, both by same author. they are both um ... questionable. more weird than this one
The abuse might be a reason but isn't an excuse. You can (and even should) feel pity for everything that happened to him back then but he's still a bad person at the end of the day. Everyone should just accept it now, especially because people around him shouldn't suffer cause of his trauma.
"I'm a pigeon! :D"