In these days of political correctness, why is it acceptable to call things (insultingly) "gay" and "lame"?

My middle school aged boys have a habit as calling things "gay"....apparantly the purse I bought last week is gay..I just looked at my son and said, "You know honey, we need to be tolerant and not judge different lifestyles-if my purse is wired to have same gender with another purse than so be it!"...yeah, my kid thinks I'm nuts..