I didn't say the theories are racist, I said they are founded in racism.

A large amount of the ancient aliens stuff stems from Chariots of the Gods? by Erich Von Daniken, who is very clearly racist.

If we look to von Däniken’s work, there can be little doubt that his racial beliefs influenced his extraterrestrial theories. After a short stint in jail for fraud and either writing or appropriating the material for a number of other books that developed his ancient astronauts theory, von Däniken published Signs of the Gods? in 1979. It is here that many of his racial views are most boldly stated. British archaeology officer Keith Fitzpatrick-Matthews points out on his Bad Archaeology blog just a few of the many racist questions and statements posed by the author: “Was the black race a failure and did the extraterrestrials change the genetic code by gene surgery and then programme a white or a yellow race?” He also printed beliefs about the innate talents of certain races: “Nearly all negroes are musical; they have rhythm in their blood.” Von Däniken also consistently uses the term “negroid race” in comparison with “Caucasians.”

https://hyperallergic.com/470795/pseudoarchaeology-and-the-racism-behind-ancient-aliens/