so through stalking the steam forums I've come to learn that quite a few people are having issues with accidently setting of the shop keeper perhaps this is a issue that should be dealt with?
(although you can continue to buy and ignore him nobody else seems to have realised this apart from me)
I think an efficient way to do this would be to have a prompt popping saying something to the equivalent of ,are you sure? with all relevant information after words,
while giving you the option to back down or to fight him like a man(or hydral I guess?).