I wouldn't be too excited about it. So he had a lot of straight porn and only a few gay/ tranny porn videos, okay. I'd be more concerned if it were the opposite. It's not uncommon to look at porn that turns you on visually, but isn't something you would ever be involved in physically. I'm willing to bet more guys look at gay and or bisexual porn than are willing to admit, because of the stigma.
You won't get him to stop looking at porn, that's an unreasonable request from you. Get that out of your head. Why do I say that? Because guys are visual!! We can't help it, we're hard wired to react to the visual stimulation, which is why we have the head turn problem with hot chicks, it's not because we're pervs, we just cannot help it.