I think it's fair to say that attacking or insinuating that gov't officials were corrupt or culpable in societal problems was taboo back in the day. It is, however, an interesting story for "Batman" to explore.
Pinguin could reveal to Batman that he's only allowed to exist, in large part, because of the corrupt Mayor and District Attorney. Bruce realizes that beat up thugs isn't the solution and so he "buys" the Mayor's office; everyone in Gotham despises him for, but he actually makes changes that improve Gotham. It could also be a redemption arc for Harvey Dent.
Pinguin could reveal to Batman that he's only allowed to exist, in large part, because of the corrupt Mayor and District Attorney. Bruce realizes that beat up thugs isn't the solution and so he "buys" the Mayor's office; everyone in Gotham despises him for, but he actually makes changes that improve Gotham. It could also be a redemption arc for Harvey Dent.