Was Willy Wonka a slave dictator?

He was a white male. By definition, he was evil.

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Where in the film did he say this?

Yup! And he adopts Charlie at the end, and takes the Bucket family to live in his giant surreal sweatshop operated by slave laborers who are trapped there!

Presumably the publishers rejected the sequel about the Oompa Loompas rising up and slaughtering their oppressor, and Mr. Bucket begging to get his job and the toothpaste factory back.

When Wonka got to their native land he basically hit the mother load. He basically found an entire race completely vulnerable to the Whangdoodles, the Hornswogglers, and the Snozzwangers and willing to do anything for anybody who would be willing to take them away from there. So Wonka, being the sadistic and evil opportunist that he is, told them they could come and live in his factory, no problem.

Little did they know, as soon as he got them in the factory he immediately had them bound and chained in the secret dungeon fortress below his factory. He then proceeded to feed them nothing but water and bread until they agreed to comply upon his terms of residency. The main term consisted of a slave labor obligation in his chocolate factory for life. They are each awarded one chocolate bar a day.

If escape is attempted or any disorderly behavior is experienced the offending Oompa is immediately shipped back to the native land and fed to the Whangdoodles, the Hornswogglers, and the Snozzwangers.