stol saidIt's impossible to change your taste with regard to the tangible.
It's not impossible, it's just difficult -- and for most guys not worth the cost, the tedium, or the trouble since more often than not it would likely require the assistance of a therapist trained in re-conditioning, reinforcement, and behavior modification. But yes, such a clinician could bring you through an arousal state and through systematic reward, systematic punishment, or systematic pairing of guys who are "not your type" -- or a combination -- eventually elicit a voluntary response of arousal with previously un-arousing types.
It is a similar to the method of therapy used to "cure" pedophilia. It's just not feasible for patterns of attraction that are not maladaptive and harmful.
But one thing gay guys could do is be more open to experience. Many gay guys will not even be platonic friends with guys who are not their type. Gay guys could be more open to getting outside their bubble and making platonic friends, and not just friends they would fuck -- it might not expand your ideas about attractiveness, but variety in interpersonal relationships is almost never a bad thing.