Watch Fox News Channel or listen to Rush Limbaugh these days and you will get a very large helping of Jonathan Gruber, the MIT professor whose comments about the "stupidity" of the American people in relation to the passage of the Affordable Care Act has reignited political debate over the law.

Gruber is quite clearly conservative catnip. But why?

The key to understanding why Gruber has become a cause celebre -- but not in a good way -- for conservatives is that his comments about the ACA confirm two things that the right has long believed about Democrats and the law: (a) The ACA was made purposely vague to keep the public in the dark about its depth and breadth, and (b) liberals think conservatives are stupid.

The first point is somewhat obvious. Ever since then-House Speaker Nancy Pelosi (D-Calif.), way back in March 2010, said, "We have to pass the bill so that you can find out what is in it," conservatives have been convinced that Democrats either (a) don't know what really was in the law or (b) more nefariously, Democrats knew exactly what was in the ACA and pushed it through Congress to keep the public from finding out.

If you believe "b" -- as does virtually every member of the Republican base -- then you see Gruber's comments, made in a panel discussion in 2013, as the smoking gun that proves you were right all along. (BREAKING NEWS: People like to believe their theories were/are right.)

Here's Marc Thiessen, a conservative columnist for The Washington Post, writing about Gruber and the ACA's individual mandate:

The reason he called it a tax is because — as Jonathan Gruber now admits — members of the Obama team knew all along that it was a tax. They intentionally deceived Americans about it because if they had called it a tax, Obamacare would never have become law. It’s one thing for Americans to suspect that their president lies to them. It’s quite another to hear a key Obama adviser boast of it.

The second point is slightly more subtle but, I think, even more responsible for why Gruber and his comments have conservatives seeing red. Nothing makes conservatives more angry than the belief, which they think is widespread among liberals, that they are stupid. That if only conservatives read as much as the left or had the intellectual capacity of the left, they would see things the way the left sees them.

"It just confirms how stupid he thinks you are," Limbaugh said Monday of President Obama's distancing of himself from Gruber over the weekend. "That sound bite is an exclamation point to how stupid and gullible Obama believes you to be." Even David Brooks, no conservative bomb-thrower, writing in the New York Times on Tuesday about Obama's struggles in his second term, suggests: "Maybe it’s Gruberism: the belief that everybody else is slightly dumber and less well-motivated than oneself and, therefore, politics is more about manipulation than conversation."

So, it's not just that the Obama administration is trying to pull the wool over your eyes. It's that they think you, conservative American, are too stupid to even notice. That's a double whammy of outrage about a topic -- the ACA -- that already had a long history of inflaming conservatives. And that's why conservatives can't get enough of Jonathan Gruber.