The majority of fags and dykes I've ever known felt it from a very young age. Certainly if it was a choice they could actually change they wouldn't knowingly suffer through all the shit that the fag-haters inflict on them.

At the same time, there are some who have said they developed a taste for it over time, more often those are bi-sexuals though.

There is no real scientific evidence for a genetic or physical cause yet though, all the reports in the popular press have been proven false by follow-up studies.