So this apparently happened (heard it through phone) and while it sounds dubious at best, he claims it really happened, and asked what he should do, so I'm asking for some suggestions now.
So he entered a donut shop, in the more shady side of LA, and upon entering, he began to look at the menu, and after about barely thirteen seconds in, a worker (apparently manager), said to "hurry the fuck up, and get out of his store." My friend asked what was his problem. After some arguing, the man responded by pulling out a kitchen knife, and said it was my friend's last chance to leave, and he promptly ran out.
He expressed his desire to take action, and I said I would get more feedback. Do you think it's worth taking action? He's not going to see him or his store again, but out of spite.