There are obvious bad/evil actors in the world. When people talk about engaging with other humans respectfully, they're generally not referring to the Putins of the world.

And it's pretty rare to have so much clarity about a person to know they're in the "obviously reprehensible" bucket.

I'm not saying this is what you're doing, but I often see people argue like this:

1. There are obviously bad actors in the world

2. Nobody would argue those bad actors should be given respect

3. So I won't respect people I come across who disagree with me

The fallacy is in the jump from 2 to 3, and the assumption that the existence of bad actors means the person I'm interacting with right now is one of them. The vast majority of people aren't Putin, nor can they be judged so quickly/clearly. And setting aside whether or not someone like that deserves respect, there's also a clear difference between respecting someone for who they are vs. behaving in a respectful manner out of self-preservation. The latter may ultimately keep you alive.