People can be born genetically predisposed to this sort of action. It always makes me laugh that it's generally accepted people don't choose to be gay and that they're born that way, but the same logic isn't applied to murderers, paedophiles and rapists.
Of course environment plays a role but there's an inherent trigger in them that isn't there (or more deeply hidden) in the majority of people.
So basically, you can be born that evil, if by evil you define it as a cognitive defect.
And before you all kick off, I'm not saying gay people are the same as paedophiles -_-
