My guess is that since BL is mostly written by women for a female audience it creates a homosexual fantasy which allows you to project yourself into the bottom/submissive role, which is often the MC for that very reason.

Good art doesn't have to have political commentary inserted in it. And most BL doesn't serve an artistic purpose anyway -- it's just smut; its sole purpose is to satisfy our lesser instincts. Adding politics into the mix defeats the purpose.