A slur is a word that expresses disdain or hatred for a specific group of people. It’s a bad word for someone who isn’t like you in some way.
There are slurs for all kinds of people — people of every race, religion, gender, sexual orientation, country of origin, and so on. I could list a wide variety of slurs here to illustrate the point, but you’ve probably heard them all.
Slurs are like other words. Sometimes they’re very powerful. Other times they’re silly or pathetic. Always, in context, they tell you something about the person using them.
Maybe what you learn is that the slur-slinger grew up around other slur-slingers. Maybe it’s that she wants attention. Maybe she believes her right to say whatever she wants at any time is more important than any pain or fear or hatred her words might sow once they exit her mouth.
Maybe she has something funny or insightful to say about language. Maybe she really does think anyone who isn’t exactly like her is not a full human being. People are hard to read sometimes.
If you use slurs for any of these reasons, sometimes people will call you an asshole without learning your life story or patting you on the back for your bravery. Maybe it’s because they don’t appreciate nuance. Or maybe it’s because you are, in fact, an asshole. Like I said, people can be hard to read.