I understand that, but the implication is there that he assumes that "because" he's met a lot of people - he's therefore finding it a spurious claim that they exist...which is an odd claim to make since they have whole online groups dedicated to their membership where they congregate. Not to mention, it's likely not the first thing you'd tell someone you've met, I would presume.
I also find it likely there's been surveys asking if folks self-identify as supremacists which would give us another indicator that they exist.
It's also odd, to me, that both the Republican and also the Democrat DHS/Justice Departments classify them as a threat...if they're just ghosts that are barely there. Not to mention videos of them. And recordings.
Just a really weird thread premise.