Very few things piss me of quite as quickly as when people dismiss homophobes as being closeted gays. This squarely shifts the blame from a homophobic society created by the majority to an oppressed minority. Their are many reasons why this argument is utter nonsense but I will first discuss how memory works.
We tend to remember unusual event more than typical events. How well do you remember last Tuesday vs 9/11? Events that are unusual and atypical produce more vivid memories. A well known homophobe such as Ted Haggard being discovered as engaging in homosexual behavior, sticks out in our mind because it's unusual and atypical and also because its well covered in the media. It makes us forget the hundreds of other homophobic pastors, rabbi's, priests and politicians who are not engaging in homosexual acts. Memory is also easier to retrieve if we have emotions attached to it. Having a Larry Craig exposed as cruising in the bathroom causes a lot of media attention, highlighting the event and making it salient. Therefore this event is more likely to stick in your head than your homophobic mother/aunt/grandmother/pastor etc. So we forget our regular mundane straight homophobes while remembering the aberrant homophobe (i.e. the gay homophobe)
Here is another reason I don't buy that homophobes are disproportionately gay. Think about your grandparents generation and how much they do not like gay people. Do you think they were a particularly gay generation? Do we really all have closeted gay grandparents? Was this the gayest generation ever? Now, think about youngsters today, and how much less homophobic they are. (according to most polls, a large percentage of young people support gay marriage). Is this a particularly heterosexual generation?This is one of many reasons i don't buy the "homophobe=closeted gay" argument.
How about cultures that are more homophobic than others? Is Iran really more gay than the Netherlands? Is Palestine more gay than Israel?
Yes some homophobes are gay. I would say the proportion is same as the population. i.e: 1/10th are GLBT.
I also find this argument highly hypocritical. When you meet a racist, do you assume they are black, or part black? When you meet a sexist, do you assume they are part woman? When you meet a xenophobe, do you assume they are part foreign? So why is it this assumption is made just for us. Yes, their are biracial bigots. Hitler is rumored to have been part Jewish, however what about the rest of Germany that went along with that genocide. Were they all part Jewish? No. Similarly there will always be some gays suffering from sever internalized homophobia, but it will always be a small percentage.
The roots of homophobia do not lie in internalized homophobia. It cannot because if there was no hatred of gays from society, an individual gay person could not have internalized any hatred. Just as straight people cannot suffer internalized heterophobia, since heterophobia doesn't exist. Homophobia exists largely because of misogyny and rigid gender roles. There are other theories as to why homophobia exists, but its certainly doesn't and indeed cannot have its roots in internalized homophobia.
It is very dangerous to make this quick assumption that homophobes are gay because it shift the blame of homophobia in society back to gay people. This way society (majority of whom are straight) do not have to take the onus of homophobia. Its like blaming black people for racism. We ignore the institutionalized homophobia in religion, law, customs are point and laugh at Larry Craig's wide stance. This is why I think this assumption is really irresponsible and blames the victims for what is really not their fault.