It should be obvious to every honest person that the other content of Thunderf00t's channel is irrelevant to the claims being made in his video about the hyperloop.
They could be right, they could be wrong, better engineers than me will tell in the end. So what? Saying something true doesn't create an obligation to listen.
In fact, if you say enough true things loudly enough, they'll cart you off to jail. It's really not a great argument.