First of all, it's a lazy insult - it's just applying a label (also known as name calling) to put people down without any context. It implies that these people are irrational, inflexible and idealistic, but with a bad connotation. He could have argued that those things are true in a more diplomatic way, and more importantly, by using evidence other than just claiming that mir is "important" or "a huge leap forward for gaming performance...". Instead, he just labels the people who happen to disagree with him as the tea party. Great.
Secondly, I think it's fair to be concerned about what's going on with mir. Maybe he's telling the truth that they just want the best solution... I think everyone, whether you want Wayland or not, would like to move away from X. So maybe mir is the right way to go. However, they failed to make the case for this in a typical open source way. Why not improve Wayland instead of going off and doing your own thing? If the direction of Wayland is awful or wrong, why not point that out? And instead of just claiming that's the case, why not try to use evidence to prove that it's the case? I have been following this closely, but have no idea what the advantages of the two proposed systems is better... but it certainly seems that almost everyone other than Canonical is rooting for and working on Wayland, which isn't really a good sign...
It's very easy to be skeptical because of all the good will they sacrificed by sticking Amazon adds in my god-damned desktop. Honestly, that seems like such a shameless land-grab for clueless users' personal data which really damages their privacy. It wouldn't even have been an issue if it was simply opt in. So, because they made that poor decision, people are skeptical, critical, maybe even a bit irrational. But that shouldn't be surprising. And even if you're being personally attacked yourself, it doesn't make it right to attack other people - many of whom aren't trying to make their contributions a business and are doing their work with pure intentions - unlike Canonical and Mark who clearly have a business angle in all this (which, in and of itself, is totally fine).
Sorry for the rant, guys. I mean, do people really think "open source tea party" is at all fair?