Forgive me for lack of recall (I was busy with 3 preschoolers during the early nineties and barely had time for a shower let alone the newspaper) but did Bush (the elder) criticize Clinton like this? I don't remember that he did. To ensure that the United States remain united, it has always been an unwritten rule in American politics that no President criticise his successor. The only politicians to violate this rule, as far as I'm aware, have been Harry Truman, Jimmy Carter and now Bill Clinton.
The modern Democratic party is populated by a collection of classless animals.
Another unwritten rule has been (since George Washington who started the tradition) that no president serve more than 2 terms. It was only a tradition until FDR disregarded it and the ?? amendment was passed to legally limit it to 2 (until FDR there was no need to do so). Until the last days of the clinton presidency where they were talking up the idea of a third term. The parallels with the two traditions are pretty striking, I think. The good guys follow them and the scum bags could care less.