Kevin Drum answers Tyler Cowan's "Common mistakes of left-wing economists?" and adds another:

Tyler Cowen has put together a list of common mistakes made by left wing economists. I'm not an economist, but I'm left wing and I comment on economics, so close enough.

His "answers" include:

I think the peer-reviewed evidence is wrong...

I'm not sure I really get this one...

Perhaps so. On the other hand, "sophisticated" public choice theories are often not nearly as sophisticated as their proponents think...

His response to No. 11 is especially remarkable:

[Cowan on Obamacare:] Failure to indicate where the "bleeding heart" argument actually should stop and at what margins we should (and will) let non-elderly people die, if only stochastically.

[Drum:] Also unfair. This is mostly a marketing issue, not an economic one. In practice, the only way to build support for universal healthcare (or any other policy) is to talk up its good points, not its drawbacks. Insisting on some Diogenic level of honesty from liberals is really just a way of ensuring that liberals will never win public support for anything. [Italics added]

Doesn't that sound sort of Leninist, or at least paternalistic? I guess "marketing" is also why the bill was developed in backrooms with all sorts of unethical, if not illegal, bargains, without any debate or opportunity to read it before voting on it.

Sorry, if we start justifying lying as a "marketing issue," a democratic model ceases to function because you deny the public the information they need to make rational choices.