This article discusses the myth that homosexuals are overrepresented in childmolesters.
As an example, extremely few molesters selfidentify as homosexuals. They may molest children of their own sex, but if they have adult relationsships almost every one of them are in heterosexual relationsships. In fact in a controversial test (selfidentified) homosexual males tested for less attraction to prepubescent boys than (selfidentified) heterosexuals. The homosexuals cited the feminine qualities of boys as turn offs.
None of this proves that straight men are more prone to abuse children than gay men. But it indicates at least that there is no reason to believe that a man molesting a child is "homosexual" in any way related to gay marriage, or indeed to self identified homosexuals.