They of course, define “diss” for themselves as well.
“Perhaps you shouldn’t litter” is a “diss”.
“sssshh” during a movie is a “diss”.
Looking at a group of them who are being really loud in public - a “diss”.
NOT looking at them when they are being really loud in public - a “diss”.
I learned 35 years ago never even to look at a loud black person in the movies, let alone shush him.