Having just had sex with my SO about 14 hours ago, I can tell you with no hesitation that yes, gay men have sex with each other.
Because never in the history of the SDMB has there been a better thread to use this line:
Pics or it didn’t happen.
I’ll remember that next. Hard to remember to grab the camera when he decides to wake me up at 1am. 
Hell, i’m bi and I have deep abiding concerns that i’m not going to have any sex. Not sure if that’s really the same thing as the OP’s talking about, though.
Your commitment to proving the existence of gay sex is commendable, my good sir!
I can relate to the OP, sort of. When I see a lesbian, there’s a part of me that can’t quite wrap my head around the fact that she has absolutely no interest in ever having sex with a man. Of course, I feel the same way when I meet a straight man. Ditto gay men and straight women not being interested in girls. I mean, how can you just write off one half of the entire human population like that?
Monosexuals are weird.
Not to go offtopic, but I wonder this about myself at times. I have zero interest in women, but sometimes think I’m missing out on part of life because of it. In the interest of full disclosure I don’t see ever being interested in women (those parts they use during sex just wierd me out) but do think people, myself included, would be happier in general if everyone were bi.
I don’t believe in undecided voters the week before the election, but I do believe in gay folks. Even here, out in the wilderness, I’ve met several.
No, I have no idea what you’re talking about.
I actually have the opposite problem. I have some people in my life that swear they are not gay, and I swear I believe them, but deep down I’m just waiting for The Talk.
The first gay friend I ever knew came into my life when I was 6 years old. By the time I was in 10th grade most of my friends were gay (they all came out during the same week.) So from a young age I was pretty much raised (or influenced, rather, by this uncle figure and my straight Aunt) with the notion that if it looks like a duck and quacks like a duck, it’s most likely a flaming homosexual. To my credit, I’m rarely wrong about these things.
So you, close friend of mine, ridiculously astute, cultured and attractive… You know how to order wine and speak three languages and ballroom dance, and yet you remain hopelessly inexperienced with women. Hell, you even moved to L.A. Yes, I know I said I believed you aren’t gay. But seriously? Come on. There is no other feasible explanation for the fact that you are a 25 year old virgin. When you’re ready to tell me, I’ll be here.
(There is only one person who told me they were gay that I have ever doubted, and that is my precious sister-in-law when she was 15 years old. I totally did not see that coming. After three years of enduring outrageous PDA with her and her girlfriend, I no longer doubt.)
Alright, some people are taking it the wrong way – as I understand it, the OP is describing a situation in which he absolutely KNOWS for a fact that Gay exists and what Gay is, but still he has this sort of weird gut feeling that comes so when he says to himself “So-and-so IS gay and DOES gay things, and that’s a fact”, there is a wave of doubt in the back of his mind, a little voice saying “No, can’t be”.
He KNOWS the little voice is lying… but it gets to him!
I say it’s not so much a “belief” as it is a state of mind in which the notion that he knows to be factual, for some reason fails to “click” in place and completely displace the doubt.
I can believe that yes, there can be in a person, through no fault of their own, such a persistent effect of conditioning-imprinting-blocking-whateveryouwannacallit in a person’s mind from their upbringing or social environment. Many people are indeed intensely bombarded with the notion that “gay” is just “some phase s/he’s going through” just at the right time in their development so that it “burns in”. The OP himself states quite bluntly he KNOWS it’s an irrational reaction contrary to facts, and it irritates him.
In a way, part of the irritation may come from the opposite direction: the OP (and other people with other such “disbelief” issues about other things) may be under the impression that if “the truth will set you free”, then once you know what is factually true then everything should click into place and the denial reaction about whatever’s the issue should vanish into the air. Alas, the human mind does not always work that way. The right answer sometimes keeps feeling not quite right and you can’t help the feeling, even as you proceed to act according to what you know is true.
As to the word “fagnostic” itself, ISTM the clear path to take to defuse it is for the LGBT community to seize the term and put it to their own uses…
Yep, that’s pretty much it.
I kind of understand. I feel that way about Republicans. 
Well OK, so I’m sitting there next to a friend of mine who is a lesbian. I’ve met her lesbian lover and she’s talking about how great sex is. For some reason, I just can’t get my head around that. I can’t imagine it. Yeah, yeah. . . I know it happens and all that. But there’s something that doesn’t compute about how enjoyable it is.
It’s totally illogical because I don’t have a problem with other people liking or getting turned on by things that are not interesting to me. I think I understand what the OP means when he says that it’s hard to believe that it’s happening. . . even though I know it is.
Are you really fagnostic? Are you sure you’re not actually a gaytheist?
Nah. I watched a guy I knew freshman year go through hell for his loser boyfriend. Nothing but love could cause anyone to act that damn dumb.
I’ll admit, it was a bit of a shock the first time one of my friends came out of the closet. This was around senior year in college. Prior to that, “gay” or “fag” was just something people called the effeminate kid in gym class who couldn’t throw a ball. No one knew any actual homosexuals. I mean it was kind of a shock. Here was this fraternity brother of mine who we would work out with, go to the J Crew outlets with, borrow hair products from, listen to him singing show tunes in the shower…
…hmm…
…I guess in retrospect, he was REALLY pretty gay.
I’m more of a lesbetarian.
I’ll never forget how I felt when I saw my parents having sex. That’s the last time I rent that movie.
More like “Heteroism.” Atheists don’t believe in God; monotheists only believe in one. Rather like the OP sort-of only believes in one sexuality, heterosexuality.
And given the amount of evidence for homosexuality, I’m reminded irresistibly of the scene in Small Gods where a monotheist priest of Om is complaining about someone throwing a wine jug at a missionary’s head for denouncing belief in the god of Wine to a crowd. “What did you expect ? The god was in the crowd.”
Personally I agree; if someone put me in charge of designing Humanity 2.0, everyone being bisexual would be part of the upgrade. Bisexuality simply gives you more options than either hetero- or homosexuality; that’s as close to objectively being superior as you can get for an issue like this.
In my opinion, that is exactly the type of irrationality that the OP is referring to as his “cognitive dissonance”. There are plenty of people who absolutley know with certainty that their parents have sex, yet when they try to conceptualize it, the idea is practically rejected.
I have a cousin who will joke that his parents had sex twice and only twice, because the concept of anyone, even his father, thinkng “Hells, yeah! I’d tap that ass!” about his mother simply does not compute.
No, if everyone were bisexual, people would gripe twice as much about the men and women who wouldn’t have sex with them. If everyone were bisexual, the specific kinds of grief bisexuals get for being so would go away, though, and I’d certainly be for that.