I found his comment off putting but also count it as a guard against sensationalism. Where this post could easily go. (or might still go)
If a topic is going to be considered not worthy of discussion because of where it might go, then we'll never discuss anything. No one was saying that being a JW was as bad as living in Nazi Germany or North Korea. Drawing parallels (while acknowledging that they occupy different positions on a spectrum) is entirely valid. When people actually take things too far or make false equivalencies or begin sensationalizing things, that's the time for criticism.
Or hell, coming in and saying something like "while Nazis used the same techniques, I do think we should be careful not to equate the shunning that JWs do to the treatment of Jews during the holocaust" would be perfectly fine. I find it difficult, however, not to take the tone of that post to imply that the entire discussion is worthless, which it most definitely is not. It's a valuable comparison that explains how influential these techniques are, and understanding that can be a great comfort to those suffering under the torment of being shunned. Realizing that your family aren't torturing you out of malice or out of any special evil, but that they're just victims of the same sort of propaganda and manipulation that people have been using for centuries - that can be a powerful step towards healing.