Lots of armchair psychologists here with their own bullshit ideas of it. Imma paste this here:

Actually there's a lot of discussion as to whether paedophilia is more of a mental disorder than a fetish/sexual preference. Some say that severe trauma or feeling powerless can lead to the urge to abuse people with less power, whether that be children (In which case child abuse, child molestation and child rape) or adults who can't defend themselves (Spousal abuse, homeless abuse, rape in general.)

Rape is also typically a power thing not a sexual thing. This is why paedophilia specifically is considered a mental disorder when they can't control themselves. They are feeling the urge to exert power over people in a fucked up way. I'm just rewording what I remember reading a while back, you can google the gist of what I've said and find a more succinct way of putting it.

I would suggest ignoring these dipshits, they don't seem to have a single fucking clue as to why comparing homosexuality with paedophilia is one of the dumbest god damn things ever. Shit, most paedophilia isn't even sexual at its core, but based on the feeling of power.