I get that question often. The idea being that our system is so perfect that it is an insult to the God of Law Enforcement to defend the guilty. In my experience this sentiment is common but without much intellectual foundation.
How do I respond? I do not believe in the moral superiority of law enforcement. I see the War on Drugs as an injustice. I see DWI enforcement as a threat to liberty. How could I not defend the victims of Prohibition or Neo Prohibition?
Furthermore, it is not my job to adjudicate guilt. Judges and juries pronounce such verdicts, not criminal defense lawyers. I present my client with options and advise. If my client believes himself guilty (or the evidence overwhelmingly points to guilt) I still seek the best outcome.
What truly scares me is defending the innocent. The idea that but for my representation a defendant could be found guilty of something he/she did not do. The fear that a jury may side with law enforcement for the wrong reasons.
Defending the “guilty” is easy, defending the innocent is much harder.