I don't know why some homophobes equate acceptance of homosexuality with acceptance of pedophilia. I can really only think of one similarity between the two, and that's that they are illegal in many countries.
Homosexuality is pretty much the same as heterosexuality. Only difference is that homosexuality involves people of the same sex, while heterosexuality involves people of the opposite sex.
As far as child molestation goes, there's several reasons why it's still illegal and taboo around the world. For one, it involves a child and an adult. There's a huge unhealthy power dynamic involved that allows the adult to manipulate and exploit the child as they see fit. The adult can use their experience, authority, age, and knowledge to manipulate the child. Even if the child "consents" to the sexual activity, that doesn't mean they aren't being manipulated, and their brains aren't developed enough to get properly understand what entails getting involved in such activity with adults.
Time and time again, the victims of child molestation have shown that it's extremely harmful to them emotionally and physically. For people to even attempt to equate legalizing homosexuality to legalizing child abuse is, in my opinion, pretty distasteful and disrespectful.