You want some real historical irony? Back when the modern conservative movement was being organized in the late 1950's by Buckley and his friends, there was something like this on the right. The
Birchers, members of the John Birch Society, were influential Republicans who thought that Communists had infiltrated the federal government so deeply that even President Eisenhower was a Russian tool, accusing him of
treason.
Buckley spent the first few years of his new political movement denouncing the Birchers, losing sponsors and allies, getting hate mail and death threats from them. He eventually won, pushing them out of the mainstream, and the New Right conservatives earned the reputation of intellectual honesty for calling out its own fringe elements and conspiracy theorists. (A lesson the alt-right should have learned if they wanted to go strong.)
The modern left is not only unwilling to call out its own conspiracy theory crackpots,
it puts them on TV as the face of their party. The progressives aren't going to build a lasting intellectual movement if they don't control their own fringe wackos. It can only last until your mainstream constituency notices you're celebrating and promoting the crazies.