I know, programming ai is difficult.
but i got a great idea, not all of the bots, bot for some.
you could ad something like a "neutral" bot that only attacks you once you attack. they could be marked with yellow color
this could even open the door to add "stronger" ai, that would only attack once someone iniciates a fight. they could be marked with a skull or something.
or areas that are Dark green that have manny zombies that start flooding you if you get to close.
and many more