Because I am not them.

I am Native American and live on our reservation. On this and every other reservation I've ever been on, there are what are called 'rez dogs' that roam the reservation. Usually these are dogs that have been abandoned, run off, etc., and are half pets/half wild. Most of them are tame enough to take the latter half of your hot dog and give you a nuzzle and a lick for your troubles, but that same dog, if you make a threatening gesture or raise your voice, will be more than happy to feast on your arm. In other words, treat them nicely and they will treat you nicely back. Treat them mean and they will respond in kind.

Grandpa used to always tell me, "You are human. Aspire to be more than a rez dog." In other words, as humans, we have the choice to rise above our instincts and treat rude, boorish people with the kindness and consideration we wish they would show us.

I don't blame you for your reaction to this person. I probably would feel the same way. That said, I'd probably choose a different path than trying to make an obviously miserable person's life more miserable.