I think Endo might be experiencing internalized homophobia which turned to liking violence...

i think you may have confused boredom with internalized homophobia cuz Endo's main issue was that when you act nice or be good, people would respond in a typical manner which he found "very boring & predictable". with all of that boredom, it was a genuine fresh breath of air for Endo when he met Takiishi & became obsessed with his unpredictability. Not to mention, he didn't seem to have any issue with liking guys upon meeting Takiishi.

ty for the explanation