I'm much older than the generation he's talking about, and I think you're entirely right. I shouldn't expect too much understanding of grubby commerce from a former English professor, but I think the affect of a salesman and of an entrepreneur are worlds apart.
An entrepreneur is up to a whole thing, and deals with mainly closed feedback loops. A salesman is at best a fragment of a real enterprise, but is often, as in the case of a snake-oil salesmen, backed up by little or nothing. The feedback loops for a salesman are frequently open, allowing all manner of bullshit.
Further, even if he were right about entrepreneurship being more common, it still wouldn't be the dominant experience, so using it to explain a generation's affect is suspicious.
Instead, I think it's much more reasonable to look at the rise of electronic communication (cheap phone calls, texts, email, chat, Twitter, Facebook). It means, in effect, that each of us lives in our own virtual small town. People end up being pleasant to each other because when they aren't, the consequences are more likely to be felt and harder to dodge.