This is Thunderf00t's "shock wave" argument, and it has survived frequent debunkings. Are we really so easily misled that slapping sciencey branding behind any poorly thought out claim will cause people to repeat it as truth?
The huge thing he forgot is... pipes are not lossless! A tube break would initially cause the air to rush in at the speed of sound, but after a few kilometers the backpressure from friction with the tube walls will slow the air to highway speed and spread out the pressure rise. The way it works out, if you're close enough to the breach to be killed by the pressure wave, you're close enough that you can't stop in time before derailing.
Huh? Who's derailing here? The problem is, again, that if just a seal breaks close enough to a carriage, you are dead. This is not comparable to a derailing which requires quite a bit of things go wrong on a normal train or the propulsion dying in this elderly chap's magnetic train.
2. Speed. 1600 km/s is pretty snappy.
Thunderf00t tends to wibble on a bit and repeat repeat himself, but he does make his point.
Relevant bits start about 6m22s.
https://m.youtube.com/watch?v=Z48pSwiDLIM
Or at 10m28s in this video:
Way too snappy. Surely you meant /h not /s
His critiques of poorly-conceived technological concepts, in particular the "Solar Freakin' Roadways" scam, and Hyperloop, strike me as largely on-mark (if repetitious and self-rightous).
I'm not familiar with any Nazi or other associations, though that would be most unfortunate.
RationalWiki addresses some of this:
http://rationalwiki.org/wiki/Thunderf00t
It has no bearing on the technical criticisms addressed above, however.
If he's dishonest (not that he's wrong, but that he's dishonest) about basic social studies why should I trust his science? Let alone his experimental results? To be fair he recently disassociated himself from the alt-right ("not") nazis. So there is that at least.
Because when the vacuum breaks then people die if they are inside. This happens to be one of the biggest weaknesses of Hyperloop. It's not a good system when a failure _anywhere_ in the pipes causes a massive loss of life. If this guy's propulsion fails then, well, the train stops gradually, not a biggie. If air enters into a vacuum tube where the Hyperloop carriage is, the shockwave will do something to the carriage people ride in and it won't be pretty.