People also use extremely offensive language (including racial slurs, but not limited to them) under drugs, alcohol etc. because the words are extreme and nothing else. Using a racial slur does not necessarily make one a racist.
I grew up with a diverse group of friends, we used every slur under the sun to shit talk eachother and still do when being idiots. Those slurs have no meaning to us beyond the comedic value they provide in their vulgarity. I'd be shocked to discover any of us were racist, pretty strange to have not noticed after >20 years.