Let me show you something that I see happening all the time:
Person 1: I hate gays.
Person 2: You’re gay!
Person 1: I am not and I still hate gays.
See how unproductive that was? It was not productive at all. It is true that some studies have shown that people who are homophobic are more likely to become aroused at homoerotic stimuli. This doesn’t mean, however, that everybody you talk to who is anti-gay is, themselves, gay or that it is a great idea to point it out to them that they might be. In fact, an increased likelihood of something happening in a study that shows a correlation is not causation; it is not even close to meaning that everybody in a group of people will display a certain trait.
The point of activism is to show the other side your perspective in a manner that allows them to consider it rationally so that they can make better decisions based on the information. At least, that’s what the point of activism should be. Telling someone that they are the very thing they hate is unlikely to do this. In fact, if they are the thing they hate, you’re probably more likely to just piss them off than to get them to see a different perspective.
I am not going to claim that I’m totally innocent here, I’m not really sure if I am or not, to be honest. However, I have noticed that in all the debate going on right now, fighting for gay rights, holding religious organizations accountable for their actions and trying to get the needs met of millions of people, this argument keeps cropping up.
Not only is it irrelevant if a particular person is gay or not in the fight for gay rights, by using that argument, you’re reinforcing that being gay is a valuable insult because you’re using it as an ad hominem! Reinforcing the negative connotations behind something you’re already trying to defend is, just in case I need to point this out, counterproductive.
In conclusion: Stop it.