I don't know many liberals like the ones he describes. Maybe it's just the examples he's using, but I suspect that changing the examples wouldn't help much.

Take my Mom, she's an old line liberal democrat. She is in favor of legalization of some drugs, possible decriminalization or others, and expanding treatment options. She knows that the prisons cost a lot of money and souls. My mom thinks that domestic spying is wrong and that the war on terror has gone too far. She is exactly a moderate suburban democrat.

I'd like to see some evidence that the kind of liberal this guy describes is a significant portion of self identifying liberals.

I'd say that it's true that almost all politicians believe the electorate is more conservative than they think it is, maybe that is where he is getting his sense of the state of liberalism.