I think by "meatheads" GP means people who undervalue education on the basis of "I succeeded without much of it" (failing to understand the contribution of a particular social context to that success) and thereby promote a culture which undermines the context which allowed them to succeed. (The specifical example he gave was people with only a HS diploma, not people without one, but I think that example was, in any case, illustrative of the problem, not an exhaustive equivalence; nor do I think "blue collar workers" is the right generalization from the example.)

There's plenty of people (blue collar and otherwise) that succeeded with only (or even without) a HS diploma that don't undervalue education, and they don't meet GP's description of the meatheads he is talking about.