Why is protectionism popular? - no comments

Here's a great round-up of the issues in the protectionism/free-trade debate. The comments are useful too.

Question is: why are we (the Labour bloggers) unwilling or unable to put the same effort in? Doesn't the world economy matter? Do we have to trust people (politicians, or popular newspaper columnists, of all people) to do all the economics for us? Is it that we don't understand the subject, or that we prefer to think in terms of political will, morality, and ideology, and - generally - the greed of economic agents?

I know of a few theories, but what do you think?