assuming you are referring to Stevie with the homophobia comment, but that was during an argument with a shithead that probably got him heated and saying dumb things, not like he was actually doing anything terrible to someone with a different sexual preference than him
Recently, I watched a fight occur between two roommates outside of a bar. One of them kept calling the other a homophobic slur as he pushed the other into a fence and tried choking him out, evidently blaming the other man for "burning up all [their] stuff." After the fight was done, a man standing around (possibly a mutual friend) raised the use of homophobic slurs, mildly censuring the man, who replied, "I was in a fight! I'm sorry!"
I also remember hearing a big news story (maybe in the 90's) about some white dudes in NY who hit with baseball bats a black man that was in their neighborhood. The white dudes were charged with a hate crime because they called their victim the n-word during the beating. Their counter to the hate crime charge was that their use of the n-word didn't have anything to do with their victim's race, but rather that the n-word was part of their regular vernacular.
The n-word has never been a part of my vernacular, but I used to use homophobic slurs on a regular basis (stopped in my 20's when I became friends with some gay men who urged me to realize the error of my ways).
I think the most compelling and altruistic reason to not use racial and homophobic slurs, when you are not part of that community, is to have self-respect and desire not to offend any member of that minority group nor contribute to their dehumanization.
But, another -- more selfish -- reason to excise such slurs from one's vernacular, if they were ever adopted in the first place, is because if you lose control and use those slurs in an altercation, you may be guilty of committing a hate crime.