"A racist billionaire[1]"

Penn Jillette has a great saying on this (paraphrasing):

"Unless the person has explicitly said they're racist, claiming someone is racist requires the power to look into someone's heart, which no one has. The KKK and stormfront are very open that they are racists, and you can call those people racist because they say they are. You cannot make these sorts of claims without putting words into other people's mouth".

And you're putting words in someone's mouth. According to that article, Thiel believes that affirmative action is not helping the poor or disenfranchised, but is rather helping the middle and upper class people. Extrapolating racism from his statements is a giant leap in logic.