You can accept homosexuality and not paedophilia, because paedophilia involves forced sexual activity without consent, homosexuality does not (except in cases of rape and so on, but rape isn't a homosexual specific issue, far from it). Similarly, with incest, any children born out of it are at a very high chance of genetic issues due to the narrow gene pool involved.
You seem to be acting from a position that homosexuality is inherently negative, whether people are born gay, or it's down to environmental factors, or a mix of both, it doesn't really matter, it's not an inherently negative thing, and is a completely natural phenomena.