BerryGirl, my Aspie has directed similarly cruel outbursts at me - under the most benign circumstances, in response to compliments, good news, or harmless questions. Each time I was shaken for weeks or months, because it was so painful, unwarranted, and inexplicable. I've known him for over 15 years, in many different contexts, so I know he's not physically (or verbally) abusive. He's my gentle giant, so why would he be so vicious? I came to understand that those were meltdowns, provoked mainly by his immediate situation, environment, circumstances, and mental state, that I could not possibly have anticipated or known about.
He recognizes that he needs to work on his anger, and I think he has. Even so, I'm much more careful to steer clear, give him plenty of space, and take care not to interrupt his routines (even though I don't know exactly what they are at the moment). I know the rage is not directed personally at me. It is not his intention to wound me. I interpret his meltdowns more like a flashing red engine light, roughly meaning "overload - not now." Nonetheless, his words cut like 1000 razor blades. I'd rather have no response or interaction at all, than be subjected to another meltdown.
I think many people misinterpret meltdowns as abuse. It's hard not to. I'd rather that he punch me in the face, than speak to me that way again. For now, my solution is to tread very lightly. I would NEVER surprise him in person - I don't even call him. Since I can't know if my timing is good or not, I always send a text, so he can read and respond (or not) on his own terms. If he doesn't respond, there's a reason for it, so I don't keep bugging him until he does.
As for your guy, spitting in someone's face is assault and battery. That's physical. That's not ok. He should be made aware of that, before he gets in trouble with the law, and learn some techniques to manage his stress and anger.