I sometimes ask my husband if he thinks a man is good looking and he will look at me crazy. I asked him had he never thought a man was good looking. He said he guess he never really thought about. I make comments all the time about how beautiful a woman is and he sometimes thinks so other times not. I guess it is what a person's opinion as to what beauty is. So I guess if a straight man never thinks of men as good looking it would seem odd to them that another man would think they are beautiful.
I have a male heterosexual friend who has told me that he recognizes beauty in men's faces, but feels no erotic allure in them. This seems analogous to the admiration many gay men have for women's beauty and grace, without feeling a concomitant carnal impulse when confronted with these qualities.
A first cousin of mine once insisted, in our adolescence, that he had no opinion whatsoever in whether a male was good-looking or not, and that this extended even to himself. I accepted his statement at face value at the time, but eventually came to feel it lacked credibility. How could a man groom himself, make sartorial choices, and generally present himself to the world without sharing some idea of male attractiveness imbibed by the larger culture? The late cultural critic Philip Core argued that no one looks more enviously at men than other men, and I suspect this trait extends to men generally, not just those who happen to be gay or bi.