Not sure where your getting the idea that you can't defend yourself from the threat of harm or realistic perception of that threat. You absolutely can.

Heck even if the perception isn't reasonable you still can. Your case is just much harder to defend.

If someone is just an ass and says YBMC to you that's probably not legit, but context matters too. If it's said in a threatening matter, that's a threat plain and simple.

As always flight should be the primary response but fighting off you can't run would be fine.

I'm the end, if you have to defend your life, then do so. Worry about the legality after. Don't let someone hurt you because the Internet said the law isn't on your side. Don't get hurt cus the cops aren't on your side, the cops are never on your side.