I think in that instance you can probably balance the disgust at a specific client/case, with the overall benefit of having a (mostly) blind legal system
I guess you must be able to fall back on the fact that everybody has a right to a defence no matter how grave their crime.
Somebody I know had to defend a man who murdered his new born baby by kicking it down the stairs. That trial was in the late 80s and it still affects him a little now.
Friends of mine specialise in family law and child protection. That can get really grim. Particularly when they get to see the inadmissible evidence after they've made sure the children stay with the parents.
I think in that instance you can probably balance the disgust at a specific client/case, with the overall benefit of having a (mostly) blind legal system