Any lawyer who gets a client off that is demonstrably (during the trial) guilty of a crime on a trivial technicality, is scum as far as I am concerned. If a cop illegally searches someone's home, finds evidence of a crime, arrests that person, and nets a conviction, the cop is apt to be told "Don't do that again, wink wink." If, however, the case gets thrown out because of the cop's malfeasance the message will instead be either "Don't do that again or you're fired," or simply "You blew it--you're fired."
Ideally, there would be some outside means of punishing cops who break the law without inflicting criminals back onto society, but history has shown time and time again that the only effective way to punish bad cops is to ensure that they don't get convictions. While it's unfortunate that the rest of society must suffer for bad cops' misdeeds, that's better than the alternative of letting bad cops go unpunished.
Okay, I can see that, even if we have strayed from the malfeasance of lawyers to that of police. Then again, you could argue that the cop's transgression was on the side of arresting the criminal, while the lawyer's transgression is on the side of lessening or eliminating the punishment of the criminal. While I cringe at the violation of privacy and illegal search and seizure laws, one might argue that the iilegal search of an innocent person's home will yield nothing, while that of an alleged perpetrator would.
A demotion or loss of overtime would be more than sufficient punishment for a cop, as it would involve significant financial penalties and functionally undo the convictions they have already gotten that would have led to their previous promotions.