I don't live in Boston, but I can take a guess that it's a combination of a few things.
1. Envy from reporters who are die-hard Red Sox reporters at heart and resent the rose of the Patriots for some reason.
2. The success of Boston as the number 1 sports city In the US is unquestionable and has driven insane expectations, so when the teams don't meet those, the reporters let rip, as do many fans. Every year, a Boston sports team does not compete for a championship in the end, is a disaster.
3. Bill Belichick. Bill just does not play the game they would like. He gives them nothing, is not intimated by them, doesn't care about them and the egos in the media cannot stand that. You clearly see that with the likes of Curran, who doesn't hide his distaste for Bill at all.
The lone exception continues to be Mike Reiss.