I certainly didn't mean to imply that people without a degree are dense or slow, some of the brightest people I know never got a degree.
My point was more than the percentage of people with degrees who might be considered "dense and slow" is going to be significantly lower than of people without education, and I would imagine the difference is further highlighted when the degree is from a university like Oxford.
I'd never suggest that person A who went to Oxford is smarter than person B who went to a less-popular university, or none at all, without knowing more about both people, I just think as an overall it works out that way (you don't have to get a degree to be clever, you do have to be [reasonably] clever to get a degree)