How about career advice?

...our boss who would literally stand in the middle of the office berating him, talking about how stupid he was, telling him he was about to get deported if he didn't straighten up, talked about f$%king the kids' new wife, etc. all at high volume so all in the office could hear. ...
Now they're telling all prospective employers that they wouldn't recommend hiring me.

...won't hire me because former employer said not to, and they have said this to others, too. ...

TLDR: So, what do you tell a prospective employer about why you left, how you left, and what the previous employer said?

F'n sue them for defamation...they CANNOT advise other employers not to hire you. In CA, that place's management would be turned over so fast it would make the stockholders head spin. There's about 6 labor laws broken right there. Don't say **** about your last employer, just tell interviewer what you did there and your responsibilities. In CA, they can only confirm your employment with your last employer, NOTHING MORE. They screwed you, Go work for the competition. You owe them nothing and sounds like you got a pretty good lawsuit to boot. Threatening someone with deportation? Oh man...so they are knowingly hiring undocumented workers? Call ICE and calmly put in an anonymous tip. Listen, they are ruining your chances of getting employment illegally. You want to take the high ground on this and just 'take the shots'? Go see a labor lawyer, many have free consultations.