Yeah, between "It's a joke" and "The author is absolutely bonkers", I used Occam's Razor and went with joke
Once you include implementations of the languages, the picture changes a bit. Once you include the standard libraries, it changes a lot (Java has some really funky attack vectors, deserilization attacks being oretty popular), and once you puddle standard frameworks on top it the game changes again, leaving PHP and Ruby pretty high on the exploitability lists (hello wordpress, hello rails).
But then again, expoitability isn't directly equatable to danger, one should probably also take severity of the system into account. "Plane falling" down is usually worse than "blog being hacked".
So if one really wanted to ban specific languages, one would have to think long and hard about what and why and how - and whether some languages
are fine, whereas we might want to purge a ton of their frameworks. I'm pretty sure PHP should be purged. I'm not sure whether any new code should be written in C/C++, but I'm also not sure whether we have languages that can fully replace them for everything.