And "propaganda outlet"? "push that agenda"? Last I heard, this whole thing was in response to a audience question when he was talking about something else entirely.
That said, I get your point, but I also think separated housing is necessary for my sanity.
Somehow I don't get the feeling he's this selfish. If that's an agenda he's pushing (which I don't know one way or another), I would expect it's because he genuinely thinks it's better for society, not because he wants to make himself feel good or rake in more profit. (To re-emphasize: it's not clear to me he is pushing this agenda.)
I'd really like you to be right about that, but the cynic in me has to assume that's what he wants you to think (car companies run by "unselfish people who want to improve the world" sell more cars).
Your carbon footprint commuting on high-occupancy diesel trains while living in a 50 year old highrise is usually going to be significantly lower than commuting in a Tesla and living in green detached house.
I think it could be a tossup, depending on how green the house really is. But making a truly low carbon footprint detached suburban house is still prohibitively expensive in some climates, due to space and water heating needs.
If you take the same green tech and apply it in a multidwelling context, then it becomes more economically feasible.
You see something similar today with Internet services like iPass that provide gigabit Ethernet service only in buildings with more than a certain number of units.
Some of this kind of thinking could be attributed to simple ignorance, because his wealth and profile deprive him of routine exposure to what he is critiquing. As others have pointed out, this is why we shouldn't treat people like Musk as having omniscience on all topics.
In Musk's case, like most people as wealthy as him, he probably doesn't ever take mass transit. His impressions are drawn from a small sample of his own pre-wealth experiences, and also from the echo-chamber of similar people around him, who might have similar experiences, and therefore he focuses on, and emphasizes problems that stand out to him without the larger context of mass transit's benefits.