Take one wooden pole, with a bird feeder on top, and a small battery-energized electric fence charger. Wind a couple copper wires around the pole and connect the fence charger.
Watch the squirrels try to climb the pole, jump off, and twitch a bit. It's, well, I'm sorry, it really is kinda funny. The current is enough to give 'em a pretty good shock, but apparently does no permanent physical damage.
I can't speak to their emotional state, except I do notice they seem really conflicted whenever they look at that bird feeder. After a few tries, they leave it alone.