You brining it up is only the second or third time I've seen someone bring up that others try to claim that Jean made Bobby gay and it's still amazing to me that people really think that. Literally all three other boys were like HECK YEAH A GIRL when Jean first showed up in the very first issue of the very first X-Men series and Bobby was like why are you all acting like animals she's just a girl who cares
It's the homophobia and the sheer inability to read. And ok, some of it is other gay people making jokes, I guess, but it still irks me on principle no matter who I hear it from.
There is some merit to the critique that since Bobby came out a lot of his actual personality has been worn away in favor of "gay comic relief with the occasional badass moment" (not to mention the terrible way in which he came out) and a sharp reduction in his focus and importance since then, but that's on the writers/editorial and isn't "proof" that Bobby coming out was a misstep or a bad direction for the character.
Like, one thing that's always stayed with me is that when I was in college, back before I was into Marvel and didn't know shit about the X-Men, I knew someone who liked Iceman and the main thing I remember about him is how insistent he was that "there's no way Bobby was gay, he's had relationships with women!" but like you said, there's that exchange in issue fucking ONE of the og X-Men run, and if you look through his earlier appearances (especially the DeMatteis Iceman solo and Defenders run which I REALLY wish more Iceman fans would read) there's a lot of threads and commentary that fit with Bobby being gay.
If you do some digging on the way back machine you can find some old fansites (like, 20-30 year old sites) laying out evidence for Bobby being gay. Whoever that fan is, I hope they're doing ok and they feel vindicated.