I think it's an individual taboo based on typical male sexuality hang-ups.
So each individual has to rise through it on their own.
With color, people just learn to accept the color as another permutation of skin color, no different than getting a tan (in practical terms). With the gay thing, there's an element of sexual attraction and behavior going on that is inherently threatening to men still formulating their own sexual identity; it creeps them out just like a woman might feel creeped out if she thought all the guys around her were potentially ogling her body. And I'm not saying that's what's going on.... but it's the prominent fear of that going on that then threatens the more insecure male.
And this might be more a pattern of individual growth to overcome, not necessarily a cultural one. Culture just can strongly enforce or unenforce neurotic tendencies by how it labels certain behaviors good or bad.
So removing general negative cultural stigma of being gay will help alleviate individual stress but will not totally remove it. If an individual saw being gay as just a variation of sexuality rather than as a perversion, then perhaps it could just be taken in stride (as race); unfortunately, gay behavior is entrenched as a perversion in certain predominate moral/religious circles, so that attitude is always going to be there for an individual to work through regardless.