That's kind of what I was getting at. No other medical/surgical stuff bothers me at all but there's something deeply primal about protecting your dangly parts as a cis man that can override a pretty strong dispassion/interest for surgical procedures. I think the only other surgical technique that's ever bothered me is when someone is getting a nose job and the plastic surgeon has a chisel up there and is going to town with the mallet like he's John Henry. That's still an overwhelmingly distant second to even the cursory thought of testicle removal to me.

It's been a fairly convincing argument because any man who can accept that trans people actually want that is generally much more open to accepting that being transgendered is real.