Before Herman Cain become known for allegedly sexually harassing women and his foolish 9-9-9 plan, the Republican presidential candidate was widely recognized for his bigotry towards Muslims.

Cain wasn’t even cautious about it. He’d rail against Sharia law; he said American communities could refuse to allow Muslims to build houses of worship; and he vowed to block Muslim Americans from his cabinet, regardless of their qualifications.

The GOP candidate has since moved on to other issues, but Cain hasn’t completely abandoned his bigotry, telling GQ that “a majority” of Muslim Americans are extremists. He believes this because an anonymous source told him it’s true.

“I have had one very well-known Muslim voice say to me directly that a majority of Muslims share the extremist views,” Cain said in an interview with GQ.

Asked if he thought this individual — whom Cain would only identify as “a very prominent voice in the Muslim community” — was right, Cain said that although he found it hard to believe, ultimately he trusted his adviser.

“Yes, because of the respect that I have for this individual. Because when he told me this, he said he wouldn’t want to be quoted or identified as having said that,” Cain said.

I’m afraid we’re well past the point of Herman Cain having any credibility on any subject, but let’s note two angles to this. The first is that it’s completely insane to think most Muslim Americans are extremists. Even the most unhinged bigots don’t usually go this far.

There are roughly 1.8 million Muslims in the United States. In Cain’s strange mind, more than 900,000 of them have been radicalized? Please.

The other thing that jumps to mind is, have you noticed how often Cain relies on secret sources? In this case, a secret Muslim-American leader told him how extreme Muslim Americans are. Who said this? Cain says it’s a secret.

But Cain keeps pulling this trick. When evidence surfaced that his campaign apparently violated federal election law, the candidate said he’d hire an unnamed investigator to look into the allegations. Who’d oversee the probe? Cain says it’s a secret. How will the investigation be conducted? Cain says that’s a secret, too.

And on his 9-9-9 plan, the GOP candidate claims he relied on “well-recognized economists” to develop the policy, but they’re secret economists. Cain added that his campaign had an “independent firm … dynamically score” his plan, but the analysis is secret, too.

I believe I once had a conversation like this with a five year old, who’d answer “it’s a secret” in response to questions he couldn’t answer.

Steve Benen

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.