Larry Kudlow says this is news to him, and calls himself a "civil rights Republican" (then why are you working for Trump?) after he's asked about longtime friend Peter Brimelow and prominent alt-right figure attending his birthday party:

Brimelow, 70, was once a well-connected figure in mainstream conservative circles, writing for Dow Jones and National Review. But over the past two decades, he has become a zealous promoter of white-identity politics on Vdare.com, the anti-immigration website that he founded in 1999.

While Brimelow has long personally rejected the label of “white nationalist,” he acknowledged to the Harvard Crimson in 2016 that his website does “certainly publish a few writers I would regard as ‘white nationalist’ in that they stand up for whites just as Zionists, black nationalists do for Jews, blacks, etc.”

Kudlow said Tuesday that Brimelow was a guest at his birthday party at his Connecticut home and is someone he has known “forever,” going back to their work in financial journalism. Kudlow expressed regret when he was described details of Brimelow’s promotion of white nationalists on Vdare.com.

“If I had known this, we would never have invited him,” Kudlow said. “I’m disappointed and saddened to hear about it.”

Vox detailed Brimelow's beliefs here:

Before Brimelow was surrounding himself with white nationalists, and, apparently Trump advisers, he was writing for National Review. He was fired in 1997 (part of what some on the far right called a “purge” of racists from the magazine). In 1999, he founded the website VDare, named for Virginia Dare, the first English child born in North America (and for white supremacists, a deeply important symbol.)

VDare describes itself as focused on the “racial and culture identity of America” and only desiring “honest consideration of race and ethnicity, the foundations of human grouping, that human differences can be explained and their social consequences understood, whether those differences are philosophical, cultural or biological.”

But VDare’s perception of itself as focused on “just asking questions” and merely “politically incorrect” is belied by the website itself and its stable of contributors, who include some of the most visible white nationalists in the movement today. That includes Brimelow himself, who has argued that America’s immigration policy is “Adolf Hitler’s posthumous revenge on America” and told talk radio host Alan Colmes in 2016 that he would welcome a return to pre-1965 barriers to non-white immigrants because “I think the US is a white nation.”

In October 2009, he wrote this:

The plain fact is that the Obama Administration has very shallow roots in historic America. It is, to put it brutally, a minority occupation government... Diversity is not strength. It is weakness... Washington has forced whites—who for most of U.S. history would have been simply called “Americans”—to recognize, if only for now at a subliminal level, that they have common interests and must act to defend them.

I suppose if you're a millionaire and you only socialize with other rich people, it's possible you never had a deep enough conversation with a "longtime friend" that you don't know he's a white nationalist -- but I don't know that you have an actual friendship, either.