The whole problem is this is a proposal. It's not even at the research stage. As such, all we can do is speculate to its advantages and/or disadvantages and a lot of questions go answered.
If Musk (or anyone else) wants to address the criticism, that someone needs to build a demonstration systems. This was done for HSR (the US even as a test facility outside Pueblo Colorado for rail research) and MAglev (the now defunct TransRapid facility in Germany, plus a couple of Japanese facilities). Once something has been built that people can observe and ride, a lot of these questions will go away. For know, what else can we do?
Musk said it himself on an earnings call: "I think I kind of shot myself by ever mentioning the hyper loop ... [I] obviously have to focus on core business and SpaceX business and that's more than enough."[0]
He had to build Tesla to prove it would work. He had to build SpaceX to prove it would work. I think Musk knew, the moment he first mentioned it, that it would be nothing but endless pedantic discussions about trivialities.
Sigh.