Some people are very forceful with animals and disrespectful of boundaries with them. I think that cats especially are good at making it clear what they would like or not like you to do.
Maybe it's an unfair criteria to judge people on but people forcing animals to do things or otherwise treating them like objects is a red flag to me.
Yeah, also forcing it to sit or stay somewhere. And getting angry at retaliation and that sort of thing.
Obviously there's exceptions like children or people who maybe just genuinely don't know how to handle animals but I think a lot show their true colours when it comes to something that can't really fight back or speak for itself like a pet.