Honestly, these quotes don't surprise me. He has a history of being overly open with the media, and frankly he sounds a bit self-serving. For the record, I took issue with this when he was a Patriot, as well. There's a reason why Kraft felt the need, after the fact, to publicly set the record straight re: their contract negotiations, and it was because Welker had already made it all public.
I still don't really understand why he gets a free pass for saying stuff like this, or for getting benched for part of a playoff game because he had to say his piece to the media, or even last summer during contract negotiations when he was talking to pretty much anyone who would put a microphone in front of his face.
The moment he left, I figured it was a matter of time before Welker started making publicly negative comments re: Belichick and the organization. This didn't come out of left field; it's who he is. Honestly, as much as I love his persona on the field, off the field I'm not sure how he's any better than a lot of other guys that most of us don't like. Sounds to me like he has an awful lot of ego, albeit with a slightly better head for PR than most.