John Mayer's Pissed Journalist Asked Andy Cohen If They Hook Up

John Mayer's pissed a journalist asked his pal Andy Cohen if he and John are hooking up -- calling the question demeaning to Andy, himself and the general public.

John put all his emotions down in an open letter to The Hollywood Reporter's co-editor-in-chief, who conducted the interview with Andy -- and in it, he says, "To suggest that people are dubious of a friendship like mine and Andy’s is to undermine the public’s ability to accept and understand diversity in all facets of culture, be it in art or in real life."

ICYMI ... THR told Andy, fans are "dubious" of his friendship with Mayer -- in other words, people think they're banging. Andy responded, "I honestly love John Mayer, and he loves me. But because we are so affectionate to each other, people don’t know what box to put that in." He also flatly denied they're sleeping together.

Anyway, John's issue is why the question was raised at all. As he says, "I'd like to think [the public is] sophisticated enough to see a relationship like ours without assuming it must include a sexual component. That turns the concept of being gay into an ignorantly two-dimensional one, which I know you know it’s not."

More humorously, the guitar great also says there's a "long and storied history" of rockers befriending gay artists/icons -- although, he didn't offer any examples.