I just noticed this on a jog in cassiopia caverns earlier today.

Slugs of all forms are "Non agressive" mobs but when you get near them they actually have "Hate" on you if you check them they will have glowing red hate on your character.

Obviously this is due to the behaviour slugs show of them using a that AOE attack if you linger around them for too long. I just thought it was a funny glitch where the system will show you have hate on a mob that doesn't actually engage you.