What I can tell you is that the vast majority of gay men are just like us, with hard-wired nipples.
Even the "straight" men I've been with react positively to the stimulation.
But those who react negatively, or have to to say it: "it does nothing for me", or "stop it", are the insecure "straight".
I still remember one of my (real) straight lovers (married, 2 kids) would go crazy every time I jumped from his c*ck to suck his nipples, would finger me like a driller.
I honestly don't understand the gays who don't like their nipples played with. Thank God, just a statistical aberration/minority.