I did not see that point made, sorry.
Nonetheless, are you suggesting that the plot could have/should have been about two, for example, effeminate clerk's at Macy's who use the dressing rooms for their 2-4 times a year rendevouses? Not the same film at all; in fact those films have been made.
BBM is a breakthrough film BECAUSE it shows that two, non-stereotypical men are/can be in love. Not in spite of it! As a result, the openness and understanding that this "thing" is not relegated to the limped-wristed, feminine types allows for a new and vitalized look at homosexual lives and behaviors.
the masculine characters neither allows the stigmatization of feminine men to continue, nor does it endorse it. Rather, it underscores the fact that, perhaps unknown by most people before, homosexuals have a range of personaolities and behaviors. This leads to a greater understanding, not a lessening. It tends to validate, not criticize.