Ive found that many friend groups in my teens and early twenties often had a bullying/disrespect component to it. Sometimes I was the target sometimes someone else was. After 24 I have never faced such situations and I don't know how common it is after that age. But I wonder how I should react as a 30+ year old guy should it happen.
Pretty much the two ways I dealt with it when younger was fighting them phsycially and making it really costly for them or simply getting away from the situation and those people.
Unfortunately in civilized society you can't pummel the shit out of someone without a criminal record/serious reprecussions and you can't always get away from the circumstances as well. It could be your workplace or something else where you are forced to interact with that person and be in that environment.
Also its seems like the more you express annoyance or have an honest sit down with the person the more they take enjoyment out of the situation. These people are sort of hollow sociopaths that thrive off a "reaction" and "control" more then anything. For them it's not necessary "childhood trauma" or something therapy can fix. It's pure entertainment and fulfilment for them to make someone else's life more miserable cause that's really the only thing that makes them feel good about themsleves.
Honestly I don't get how you're supposed to react as an adult.