Dealing with difficult people is not easy. But learning how to do so is how we develop skillful means.
Much of it comes down to learning how to establish limits. We avoid doing so because we know when we do, it will provoke a fight with the difficult person, and we don’t want to deal with that, so it seems easier to just go along. But because we just go along with their dysfunction, it keeps coming again and again and again. The sum of all these little dysfunctions far outweighs the more extreme, but short-lived problem of them being upset when we establish limits.
It also doesn’t help them for us to allow them to continue to create negative karma for themselves; so setting limits, if done correctly, can be an act of compassion.
“Everybody welcome” is the essence of the Kadampa way of life, but that does not mean their delusions and harmful behavior are welcome. There is no contradiction between saying “you are welcome, but these delusions or negative behaviors are not” because we make a clear distinction between the person and their delusions. If the other person says, “if you are going to establish such limits on me, then I’m outta here,” you can say, “that is your choice. If you change your mind, you are always welcome back.”
All of that being said, of course we need to pick our battles. It’s usually best to focus on small things that are highly representative of larger patterns. But if that is too hard, start with the most harmful and the most disruptive behaviors.