Keep your head up and your back straight, look towards the horizon, walk with a certain pace.

Yes, that's what I usually do. (Sometimes I give them trivial amounts of money like €0.50 instead.)

I keep an attitude that if someone is manipulating me like this, I owe them nothing socially...

Yep... People trying to dishonestly manipulate me trigger a heckuva memetic immune response, akin to refusing an offer in the Ultimatum game.