Sure, I agree. But there are some kinds of diversity that no industry needs. You wouldn't, for example, ever say, "Hey, Silicon Valley is full of non-racists. Let's get some more racists in here!" You'd instead be glad that Silicon Valley had a non-racist groupthink. The same is true of things like climate change, where "diversity" just means someone is dangerously wrong and living in the past.

I don't intimately know Thiel's political views (above were just examples), but it seems that many people are worried that Thiel falls into that category of "diversity we don't need".