"Repair my car or I'll kill you," says the customer.  The manager responds:  "How about I punch you in the face instead?"  And does so.  Insurance coverage for the underlying civil assault and battery claim?
Yep.  Or at least the potential for coverage, and hence there's a duty to defend.  According to Justice Johnson, who holds that even deliberate self-defense would still constitute an "accident" under the policy.
Seems about right.  Still, unless you want a punch in the face, I might shy away from Glendora Tire & Brake Center for a while.  Or at least not threaten to kill anyone there.