MSNBC is being called on to sanction Morning Joe contributor Pat Buchanan for his anti-gay remarks.

The Human Rights Campaign (HRC), the nation's largest gay rights group, joined media watchdog group Media Matters on Thursday in calling on the cable network to take action against Buchanan after he called homosexuality “unnatural” during a Wednesday interview on National Public Radio (NPR).

“I believe that homosexuality is – that it is unnatural activity. Unnatural and immoral,” Buchanan told Diane Rehm, host of The Diane Rehm Show. “I would say that kind of conduct should be discouraged in a good society, in a healthy society.”

“And it used to be discouraged. And I do think that the idea that men can marry men and women marry women in the USA is a sign of a civilization in its final throes. I mean, we saw things like this at the end of the Weimar Republic. Things like this at the end of the Roman Empire. And they are attendant to a declining nation and a declining civilization.”

HRC disputed Buchanan's assertions, arguing that “every credible major medical and metal health organization in the United States has stated that homosexuality is normal.”

“While Pat Buchanan is free to hold and express his views, the fact that MSNBC has given him a public platform to spew this sort of dangerous rhetoric is unacceptable,” HRC President Joe Solmonese said in a statement. “MSNBC should sanction Mr. Buchanan, as his extremist ideas are incredibly harmful to LGBT people around the world.”

(Related: MSNBC's Pat Buchanan says gay marriage is being imposed dictatorially.)