because until you can change the hearts and minds of millions of people, then it's always going to be one of them.
You're admitting to being one of the millions of people that votes and therefore legitimises the construction of concentration camps.
You're a fascist.
Even strict dictatorships have elections to gauge how much support they have. They're limited in how far they can go before spawning a revolution. Just because votes aren't capable of inacting actual change against the ruling class's interests doesn't mean it isn't useful. By voting for a third party you're showing solidarity with the movement and demonstrating how the current system is a sham. By voting for the system you only legitimise it and give the rulers the excuse to say they're acting legally and with the will of the people.