I didn't endorse nor speculate why. It's a long accepted sentiment based on psychological and cognitive reasoning studies. It's not theory, it's an observation. A theory would be the proven results of a hypothesis. In this case, perhaps that might be the hypothetical that being more educated makes you see more angles of a topic because you've developed better problem solving skills. Or something like that.
I further said that in my anecdotal experience, from talking to other fans of famour authors (including SK), the general consensus is they tend to be more progressive. That is also not a theory. It's my personal observation. Not scientific by any means. I can't talk to every single person here or in any writers group of fans.
I have not found that to be the case.