Everything is a slur. It’s not about the word, it’s about intention and usage. Everyone who is fine with idiot but gets karen-y at retard does not care about people of reduced intelligence but only about oppressing those around him and making himself feel superior.
What do all those asterisk and numbers mean? I feel like I’m missing a key to decode that.
Edit: Damn, that little post lead to an actual TIL moment. I’m actually going to copy all your answers for future reference, since I enjoy etymology and get into contact with these symbols a lot. Thanks, everyone!