It's tough to defend Willie. They blew the NLCS in 2006. They had one of the biggest collapses in 2007. And they are severely underachieving in 2008. You can't fire the players, so the coaches have to take the hit.
It doesn't help that the Mets have the highest payroll in the league and have (on paper, anyway) a lot of talented players. SOMEONE has to be a scapegoat when they fail to win regularly, and Willie was elected.