It is simple. Most of us Open Source developers aren't generally good with average people. We are good with our "breed" of people but move us out of our element and suddenly we can be awkward, offensive, and generally weird. We talk differently than other people, we have inside humor that doesn't span directions, and are just as inclusive as the richest Skull & Bones society members. Is this bad? No, it is reality. Whenever you take a group of individuals who are on a different playing field than the average person you are going to end up in this situation.
The second point that Bruce states is that closed source users have very little interaction with users. I think this is misunderstood. To say that Open Source has more interaction with users is, in my opinion, completely false or is at least given much more weight than is reality. Ask any consultant: the majority of their customers have zero idea about the workings of the community, how to communicate with the community, or interactions with developers. Frankly, they don't want to. They have software to run, businesses to operate, and employees to pay.
This can be further illustrated by watching the community. It tooks PostgreSQL years longer than it should have to get replication, and the community is just now starting to look at logical replication, features that were available in closed source versions of PostgreSQL and as open source addons years ago. The users wanted integrated replication but the community wasn't willing to implement them at the time.
Please don't get me wrong, I love Open Source. I love Open Source development. Heck, the only closed source software I run is to play Civ5 occasionally. Everything else is Open Source but I do think that we need to keep perspective on what is going on in the very large world that does not involve Open Source. It is much bigger, in a lot of ways more productive, and employ smore people (a rarity in today's economy) than Open Source could ever hope to.