He enjoys bullying strangers on the internet.
Well, everybody needs a hobby.
It depends on whether PitViper is part of the VeRO programme.
In any case, DO NOT RESPOND.
That encourages his hobby.
And put him on your Blocked Bidder List.
Hmmm-- check to see if his ID is a seller of sunglasses. If he is, you might consider Reporting him for auction interference.
If the listing is Fixed Price, add Immediate Payment Required, which tends to discourage scammers and vigilantes.