I can't fully speak to their credibility, but I doubt it's an attack on HN users. I've heard of them outside of HN. If it is an attack on HN users specifically, then they're playing the long con. The first post to HN was 6.5 years ago.

https://news.ycombinator.com/from?site=dns.watch

Previous discussion: https://news.ycombinator.com/item?id=8060156