You don't see communities created by boys for boys on any topic whatsoever; that's not unique to this one subject. Boys don't go around creating online communities, they typically inhabit the communities created for them by corporate entities. Thus, that's not much evidence of anything.

However, I do have quite a bit of evidence to the contrary. There are countless accounts of boys who had such feelings growing up. Pick up virtually any autobiography from a gay writer and you will find those feelings eloquently illustrated. It's also a constant theme in gay fiction, including film and literature. Gay bookstores are replete with such material and if you sit down and chat with any gay individual about their childhood crushes they will undoubtedly talk about the crush they had on their math teacher, how they loved watching Baywatch because of the scantily clad Hasselhoff, or how they watched Legends of the Fall over and over again to get off on a nearly naked Brad Pitt. This isn't a well kept secret that you need to dig deep to find, it's fairly common knowledge that is readily available. If you haven't seen it, it's because you haven't looked.

It would appear that gays far outnumber BLs. Thus the number of young gay boys out there wishing they could have a sexual relationship with a man is almost certainly larger than the number of men wishing they could have sex with boys, and that's without even considering those boys who aren't gay but have that desire.