It's not being straight, it's totally being a lesbian.
Oh wait, you meant "straight" as in "straight man who don't know that half the people who watch porn are women" ?
This being said, how the fuck do you masturbate if you dislike penis so much ? And are you fucking eyes closed, or in deep darkness, if you dislike this much seeing a dick pound whatever girl's hole ? There's nothing more natural for a man than seeing a dick.
Of course, in porn the one you see is rarely yours, but it's not seeing it that turn you on, it's what its doing. In "a dick is pounding a vagina", it's not "a dick" the relevant part, nor it is the part I fap to, it's the rest of the sentence. Normal males achieve relatively easily to make abstraction of the dick, and only see a pounded vagina. Exactly like they achieve to make abstraction to the fact that masturbating is nothing more than enjoying to its fullest touching and stroking a dick... Guy, it's so gaaaaaaaaaaayyyyyy.
Oh, I hope that my last sentence haven't killed your desire to fap, poor little snowflake.