The illiberal left tries to paint Dave Rubin as a “dangerous right-wing extremist” because he is a bubble burster. They don’t want left-leaning folks to be exposed to him via guests like Mayor Pete because if those liberal viewers see Rubin’s other interviews, they will realize neither he nor his other “boogie men” guests are actually “dangerous,” “extreme,” or “far right wing.”
Rubin (among others in the Intellectual Dark Web like Jordan Peterson) helped me break out of the leftist bubble, so people still trapped inside the bubble feel threatened by someone like Rubin who is able to help burst political bubbles. (On both sides, by the way.) Just as he bursts liberal bubbles, he also bursts conservative bubbles, bringing both toward a more reasonable center. Dave is not a right-wing extremist; if anything, he is a centrist extremist (if there can be such a thing.)
The far-left and far-right are engaged in a full-out ideological war, but their biggest threats are not each other—it’s centrists like Rubin trying to make peace. It’s extremely rare and difficult to turn a far-left liberal into a far-right conservative, but both can easily be turned into reasonable center-left liberals and center-right conservatives, able to compromise with each other and find common ground. This is why far-leftists like Carlos Maza view centrist classical liberals like Rubin as their biggest threats. Actual far-right people are non-factors to leftists. No one in their bubble will actually be radicalized that far right. But they can be de-programmed from the left-wing groupthink and become more centrist, refusing to buy the propaganda the leftists peddle.
This de-programming/bubble-bursting is what Dave Rubin and much of the IDW is doing, which is why Vox, HuffPo, Media Matters, the New York Times, and others still trapped in the leftist bubble view Rubin and others like him as "dangerous." Rubin is especially dangerous to them because he’s gay and Jewish, so their normal gameplan of playing identity politics and calling all opponents to leftism "homophobic bigots" and "Nazis" won’t work. Instead, they call him a “gateway drug” to far-right extremism. They're half-right. Rubin is a gateway, but not to the far-right and bigotry. He’s a gateway out of the irrational illiberal left bubble to a reasonable rational liberal center. When you’re at war, a bigger threat than your enemy is the people on your own side trying to make peace.