This is a basegame mechanic btw. we just happen to add many lords to the game. I can't recommend it either.

There is one current bug with executing bandit lords, who keep non-stop declaring war on you, but yeah losing relations with everyone is normal, same thing in vanilla depending on their traits.

Also executing a lord will permanentely remove him, and there is no way for new lords to be born or made so i'd just avoid it for now.

Yeah, I found out the hard way lol.