It’s easy to get people angry when you convince them all their hard work meant less than they think, and even easier if they think someone else got something without having to work as hard.

We see this in all animals that understand fairness, and it’s the fastest way to turn monkeys against each other (visibly give away grapes unevenly if you want somebody’s face to get ripped off).

It’s also a very primal manipulation tactic that works quite well, so long as you can redirect the animosity.