It's not just Halo. He just makes declarative statements about anything - the last one as anime and basically antagonizing all the animu nerds who follow the site, to the point where people are sending him DVDs now.
The thing is, I don't think he believes these things. Like when he insists MGS is not anime, that sounds like it's just him trying to maintain his character's word view. But if every week is just going to be Dan saying "random subject X is shit" and people freaking out about it, it's just going to be tiresome to sit through.
You say he puts things out there, which is true, but the way he does it makes it feel like... well, troll bait.
Maybe he's figured out that if he says something is bad, people will send him free stuff. But for these Metro games he's clearly given it a fair go and believes it's just not for him.