Good Question!
I wish I wasn't in a rush (what's new?), I'd like to spend more time on this question.
I discovered my Dad's porn stash at quite a young age (maybe 10, I can't remember now).
Sometimes I think that's part of the reason I waited until age 35 to have sex for the first time (because I learned to use masturbation and porn as a crutch) in my early years...
...but that's a different topic actually.
The point is, I started out feeling "straight" and looking at "straight" porn mags, but as I got older (teenage years) and I got bored with my Dad's stash I would search out other forms of porn. This became my only sexual outlet.
Yes, over time I found myself attracted to the men in the videos, but it TOOK years to sort of realize why....When I was younger and using porn to facilitate sexual fantasy I would SUBSTITUTE myself for the guy(s) in the porno (mag or later video).
In other words: I wanted TO BE that guy, good looking, usually smooth, with a big dick, slaying the women (so to speak). And that sort of "admiration" (I guess, for lack of a better term) evolved into a full blown male attraction.
This is part of the reason why I call myself bi-.
I was initially attracted to girls, but so introverted and withdrawn that I came to rely on porn...
...really running short on time here...
I'm just saying, yeah, in my younger years when my ideas of sexuality were being shaped it was mostly due to my use of fantasy and porn that explains why I was more interested in the guy than the woman.
Gotta run.
Ciao.