^ Apparently subject lines are unfiltered.
I voted no.
You hear stories of people who are

but dated/married the opposite gender due to social pressures and what not. Don't know if/what social pressures could make it go the other way (e.g. straight people dating/marrying the same gender); just pointing out that there's reasons for people to go opposite of their natural inclinations.
People enjoy themselves with objects, can't say that proves they have a specific sexual attraction to the objects themselves. In the same way I can't say it proves a man is, or it causes him to be,

when he has

sex. The two are not
quite the same thing.
Of course, lets say someone -does- like the same gender in
that special way. 
They still might not want to be labeled

. You never see in the tabloids, "Could it be that <celebrity> is actually
straight?" Guys don't give each other crap by saying, "OMG, you're so straight!" You never hear about "the heterosexual lifestyle". You don't have to "come out" about being attracted to the opposite sex - it's assumed. You don't need to tell people "I'm straight", you say, "

That guy's cute," or, "She's hot," or, "I'd like you to meet my wife." If I liked girls I'd want it to be left at, "I like girls," without being called a lesbian the same way I would say, "I like guys," without people remarking, "You're a heterosexual?!"
So, yeah, if a guy wants to call himself straight, whether he likes other guys a little, a lot, or not at all, regardless of what he does/doesn't do with them, I say go ahead. It's a private feeling, so... yeah. Plus there's the fact that

sex is 100% effective at preventing pregnancy, so probably some people who'd rather go hetero do it for that reason.