Some readers took issue with yesterday’s post that characterized a carbon tax as a terrific but politically unlikely proposal, after the Obama administration shot down the idea last week. Putting a price on carbon emissions is, after all, generating renewed interest from across the ideological spectrum. Notably, the libertarian American Enterprise Institute is co-sponsoring a forum on the issue today with the left-leaning Brookings Institution, Resources for the Future, and the IMF.

And yesterday, Grover Norquist told the National Journal that the blood oath he extracted from a majority of members of Congress not to raise taxes wouldn’t be violated by a carbon tax — if it was accompanied by lower income taxes.

(Here’s the list of pledge signers in the current Congess [PDF] but here’s a tip: It’s quicker just to look at what Republicans didn’t sign — just 13 of them — and what Democrats did — just three. The numbers are lower in the next Congress, as politicians increasingly campaigned against the idea of making a pledge to Grover Norquist, instead of their constituents.)

Norquist only opened the door a crack, however. “It’s a conversation about what color unicorn you’d like,” he said of discussions about how to structure an income-for-carbon tax swap. “It would infuriate taxpayers.”

Apparently it also infuriated the American Energy Alliance — the political arm of the Institute for Energy Research, a think tank devoted to the promotion of fossil fuel development that’s funded in part by the ultra-right Koch brothers and their donor network.

“Grover, just butch it up and oppose this lousy idea directly,” AEA wrote in their daily newsletter today. “This word-smithing is giving us all headaches.” (Note: I don’t regularly read the AEA’s daily newsletter, so a hat tip goes out to ThinkProgress for breaking this news.)

If “butch it up” means “kow-tow to your benefactors,” then yes, “Grover” did just that, within hours. His group, Americans for Tax Reform, has now unequivocally stated its opposition to a carbon tax and promised to “work tirelessly to ensure one does not become law.”

Well, that’s a quick turnaround from saying that it wasn’t a bad idea.

Apparently a carbon tax is verboten now that the Koch brothers don’t like it. The Americans for Tax Reform statement calls it “big government” that will “forever damage the American economy” and “inevitably lead to higher taxes.” Norquist himself said, “there is no conceivable way” that such a tax wouldn’t violate his sacrosanct anti-tax pledge. Those statements directly contradict his assertion to the National Journal: “It’s possible you could structure something that wasn’t an increase and didn’t violate the pledge.”

The Obama administration has stated that, despite rumors circulated by British bankers, it was not planning to introduce a carbon tax. That assurance isn’t enough, however, for another Koch-funded think tank, the Competitive Enterprise Institute. CEI is suing the government to gain access to emails, just to make sure the Obama administration is serious about failing to take the single most effective step to prevent catastrophic climate change.