In the wake of the ill-fated attempt to use a government shutdown and the threat of default to force Barack Obama to defund the Affordable Care Act, conservative activists are fighting among themselves about whether this strategy, masterminded by Sen Ted Cruz (R-TX) and initially opposed by many leading Republicans, was wise.

The infighting has grown tense in some quarters. On a list serv informally called the Repeal Coalition List, comprising about 200 leading conservative activists and writers, one prominent right winger recently compared those who forced the government shutdown to terrorists.

In an email reviewed by The Daily Beast and dated October 17, Ryan Ellis, the director of tax policy for Grover Norquist’s Americans for Tax Reform, declared, “the Repeal Coalition was hijacked by Defund terrorists. They flew the plane in a new direction and assured us that x, y, and z would follow. Not only did they not follow, but in fact a, b, and c happened.”

When more liberal voices, such as Chris Matthews and Al Gore, have compared Cruz and his cohorts to terrorists, they’ve come under attack from conservatives.

Ellis declined to comment about the email, saying that the list is private. Publicly, he has expressed outrage about Cruz’s so-called Defund strategy. In a recent piece for the Daily Caller, Ellis wrote, “Much like the Vietnam War, things didn’t go quite as planned for the self-appointed ‘best and the brightest.’” In a recent tweet, he described Tea Party activists as “freakin retarded.” A few hours later, he apologized for his choice of words, saying "I used language I shouldn't have."

Ellis’s comments are especially surprising because of his position at Americans for Tax Reform, a group that fought tooth and nail not only against Obamacare, but against almost all major federal social welfare programs. The organization started by Norquist is a forerunner to the Tea Party. Its strategy to get all elected Republicans to sign a pledge to never raise taxes is very much in keeping with the ethos of the Tea Party to shrink the federal government by depriving it of revenue. Norquist has also been a vocal critic of the strategy to force a shutdown, albeit in somewhat less strident terms than Ellis.

Nonetheless, some conservatives think Ellis went too far. “Language like Mr. Ellis’ is so out of line. It’s an unfortunate outlier in the debate in my view,” said Tom Fitton, the president of Judicial Watch. “Obamacare’s strongest critics would not have predicted the almost immediate collapse of the healthcare insurance market as a result of Obamacare….it would counsel for a defund effort or another major repeal effort now.”

Editor's Note: This story was updated to reflect that Ryan Ellis apologized for his tweet shortly after posting it.