I believe being "gay" is more a mentality thing than it is a sexual thing. If two men love each other, live together, but never have sex - are they not gay? I'm also betting that the man that sucks cock in prison to keep himself from getting beaten doesn't think he is gay either, but some here would say he is.
I prefer not to live by labels. I do what makes me feels good. If you need to "categorize" than so be it. It comes from the fact that people have a desire to put themselves one step up above the rest.
In all reality this is a very deep well and debates would go on for ever, tempers would flare, names would be called, and tears (or *******) would be shed.
I think that scenario has been debated on this site before. For what it's worth, to me, that scenario is akin to *******, and a man that is ******* into male on male sex would not be considered gay, or in my mind bisexual. Self-preservation changes the rules, whether he does it one time to save his skin or multiple times.