If I come into your business and your medium to large dog gives every indication that it's about to come flinging over the top of a 4' counter to savage me...it may not go well for Fido.
I won't run - both because at several levels I can't, at least not well enough to outrun any but the most feeble of dogs - but I will drop into a defensive stance as I reach for some tools of serious social interaction.
As it happens, had this occur over lunch today - stopped in at a vendor to talk about an order, and dobie-lab mix went simply ape that someone dared to enter their owners store. Can't say I was much amused.
Doggie-parents, if you are taking your "big enough to do real damage" doggie into public spaces...for the good of your dog, make sure they aren't going to put folks at reasonable fear of injury. We may not respond well.