Here's one explanation, and it is based on the fact that there are two types of economists out there.
All economists are impressed with and convinced by the efficiency and desirability of free markets. The field is practically unanimous on this point (which is nice to see in a science!). There are two ways to take this:
- One group of economists, because they are impressed and convinced by this, like to spend their time in more informal settings (like the blogosphere or the media) telling people more about this.
- Another group of economists, because they think that point is settled scientific fact, think that the more interesting discussions are in the gray areas and the technicalities, so they figure their time is better spent there than belaboring the obvious.
This, I think, helps explain why Don enjoys blogging about how capitalism is great because it gives us dishwashers and Paul Krugman enjoys blogging about fiscal policy at the zero lower bound. Paul Krugman could have posted every single one of Don's "cleaned by capitalism" posts, but it's Don that keeps churning them out. Krugman shows almost no interest in writing posts like that even though he probably agrees with all of them. Why? Because different things attract their attention.
This is not to say there aren't differences in economists' opinions. Of course there are! But I think the way these two attitudes express themselves in the public sphere makes the field look a whole lot more splintered than it actually is.