I was friends with a guy who was really into InfoWars in the early 2000s. I'm no longer in contact with him for unrelated reasons but I have to think that keeping friends who weren't in that world helps people from falling deeper into it.
Isolating people from good ideas doesn't seem like a great way to change minds.
That person who can easily be influenced to be a white supremacist doesn’t feel accepted. I don’t really mind accepting people and opening up to them about my own flaws and ideological inconsistencies. Some people are going to fall into the wrong crowds - you can’t win everyone over, but blocking someone out because they’re superficially racist or they have “regressive” views or whatever else is a great way to get a confused person to be very sure about those views.
Additionally, I find the thought process of the person that wants to shut down those "dangerous" ideas pretty repulsive. It seems implicit to me that they are trying to protect those that are lesser than them. There's an implicit superiority there.