Having a mob not attack the person who spawns it, but everyone else.

So I have a mod that I've dropped, but I want to pick it back up since i have many downloads and haven't done an update in months. Its a mod based off the anime JoJo, with stands that are basically a spirit you can summon to fight for you. I want to make the AI so that way you dont have to make the stands hit each other to fight, so two questions: A, can you make a mob (lets just call it a stand) attack everything or every player except the player who spawns it, and B, can you make a certain category of mob called "stand" or whatever and have the stands only attack other mobs of that category? This would be a great help to me, as it would literally make my mod superior to the most popular JoJo mod.