I think it goes beyond nihilism and into solipsism. If they haven't personally experienced it, it doesn't exist. Also, if they have personally experienced it, even once, it is universal law that happens all the time to everyone.

It's the type of thinking you'd expect from a small child, and there's a reason for that. Progressives never mature past that stage for whatever reason. Maybe they have brain damage, maybe they have psychological issues, but for one reason or another they're permanently eight years old.