BUT, that doesn't make a defense attorney's job any less noble.
Let's be clear here, we're not talking about people charged with something he didn't do; representing that person is clearly noble. We're not talking about someone overcharged or in danger of being over-punished; representing that person is noble. Nor are we talking about representing the immature, the mentally ill, a person who steals to eat. It is clear that standing between society and these people is intrinsically noble.
What we're talking about here is a Reviled One. Picture the most deservedly hated person you can think of. This is the person we're talking about (someone like the BTK killer, a 9/11 terrorist, the guy who ambushed and killed the four officers yesterday). He is a member of the small group of deservedly reviled and there is nothing intrinsically honorable or or noble in protecting him from society.
And yet, the defense attorney who takes that job and does the absolute best he can in defense of that person is noble.
(1) Because these cases are the ones which pose the greatest danger to society. If there isn't someone out there fighting tooth and nail for Reviled One these cases will inevitably end up with losses of rights and protections. These are the cases wherein everyone is going to cut corners, ignore rights, and crush protections in order to get to vengeance as quickly as possible. Someone has to stand in front of that bulldozer and frustrate its destruction of the rights and protections of all on the way to destroy the Reviled One.
(2) Because there is no way that society can be just if the Reviled One doesn't have the ability to access, understand, and properly avail himself of all the societal protections. A defendant cannot really represent himself well in court. Even if he is bright, he isn't experienced. Legal research is fairly arcane and even if he has access to a decent law library in the jail (unlikely) he is almost assuredly going to miss important things. He doesn't know written court rules. He definitely doesn't know the unwritten rules of practice, which vary depending on State, region, courthouse, and judge. Without an attorney even the brightest, most capable person is not going to receive a fair trial. By giving Reviled One all the access to laws, rules, procedures, and protections he should have the defense attorney provides an honorable and noble service.
Defense attorneys do serve justice. One could even say that they "seek justice" just as much as any prosecutor does. And I now say it. Defense attorneys seek justice. It's not the straight forward justice that prosecutors enjoy. It's a more esoteric form. Defense attorneys advocate for short term injustice and in the process they assure societal justice in the longer term. That's either seeking justice or having it occur as an unintended, collateral consequence. Forgive me if I'm a bit of an idealist, but I choose to believe that defense attorneys are seeking overall justice, not just providing it by accident.