I'm pretty sure he based the decision to buy AA on that he got to play it for 2/5 hours. And also he isn't saying they are immune to criticism because they care about the game, he's talking about non-constructive criticism.
He states that the community should pre-order AA as a sign of support for Relic, and the majority of the post recounts the merits of the development team, with only a tiny snippet about how he played, but can't talk about, the game and enjoyed it. It's a very emotional appeal to the community.
If he had said people should pre-order AA because he played it and thinks it's worth the money, there's nothing wrong with that. But he added that the pre-orders should be done to support the developers, and that's what I disagree with. It dilutes what was otherwise an excellent post with an excellent message.