It's not the education itself that forms the barrier; it's the view of oneself as intellectually driven and capable of holding one's own in matters of intellectual discourse. That surety usually, but not always, comes to people via higher education. In my dad's case, it came through self-education; he's done enough reading to have an M. Div, without actually having the courses to go with it. He's not intimidated by intelligence at all.

I also think that this is a classic issue of social constructivism. Is the lack of a degree holding someone back because they don't believe they're capable of anything else, or because society doesn't see them as being capable, or is it a bit of both? I suspect that much of the time, it's a bit of both.