I think the way men masturbate can create a penis-fetish in them, since they are associating the sight & touch of an ejaculating erection with the feeling of orgasm. I think there are number of porn categories that are outgrowths of penis-fetish, like "big dick" & "BBC" & "compilation" (which just compiles male ejaculations). Back in the day, a lot of guys would admit to "skipping to the end" of the porn video, which in most cases is just the guy masturbating himself to completion i.e. 100% gay porn.

I think penis-fetish can lead to vagina-envy, which manifests itself in men anally penetrating themselves or seeking out being penetrated by others. This could potentially lead to AGP.