Well, in reading both the OP's and your postings, I agree with both; I actually think you're saying much the same thing. Most of the "incomplete" things you bring up were things I interpreted the author to mean, either directly or implicitly.

I don't think we're saying the same thing - and I don't think he really meant that.

We're talking about two different things: being isolated and being insular. The author attributes small-town adherence to conformity as a consequence of being isolated: not being exposed to other cultures, people, or ways of thinking. I think it's more of a structural consequence of being a small community: even if the people in a small community are exposed to lots of people that think, act, or believe differently than they do, as long as they're members of a small insular community they will be under enormous pressure to conform to that community's norms.

What the author attributes to lack of exposure I believe is an inherent structural outcome of the size of the community. In a big city, you can reject majority norms without serious consequence. In a small town, you can become an outcast, and the opportunity costs to you are enormous. If you're in a small liberal town, with worldly and cosmopolitan values, the same applies - if everyone in your community is composting and recycling and using mass transit (all to fight climate change), you'll pay huge social capital costs if you buck the dominant norms.