Good point. The words themselves mean, of course, different things. However, pedophilia often leads to pederasty, when it concerns homosexual men, so they are definitely related.
I'm sure in ancient greece there were men who preferred women to boys, or even grown men to boys, but also men who desired young boys exclusively, or above all others. Thus both pedophilia (for boys) and pederasty co-existed and were tolerated in one basket (or period) if you will. Both leading to the abuse of the young 'uns who need our protection, so the concern is justified in one sense.
That is why, in my opinion, it can't be made clearer to all concerned that modern gay rights movement has nothing to do with tolerating either pederasty or pedophilia.