As many have already noted, our politics weren't always so pointedly cowardly, and given the preponderance of supposed legal minds in the Senate one has to wonder at the silliness of the position. John Adams took on the task of defending British soldiers after the 1770 Boston Massacre; most were acquitted. Abraham Lincoln was a defense attorney. And yes, sigh, Chief Justice John Roberts also did defense work for an accused murderer, so we don't need to go back quite as far as all that or refer to people as iconic as Adams or Lincoln to find a time when defending people because that was your job was understood, by our top legislative minds, to be the point of the thing.
This episode is yet another reminder of how higher politics self-selects for horrible people. If you are willing to take on the task of defending someone controversial, As Is Your Damn Job, a job required by our Constitution in order to make every other gear of the American justice system work, you run the very real risk of being blacklisted from then on. Instead, it is the people who never risk such things, or who decline the tough jobs, or who pad their resumes with safer (corporate, preferably) work that are allowed to rise up the ladder. Those people become senators, and quiver at the thought of anyone in government ever doing a braver thing than they themselves would.
Good Gawd, dear senators, show a little spine. If you don't like a man because you don't like him, say so, but if we are now deciding that none can be a part of government if they once defended an unsavory character then we should expunge all the oil company lawyers, tobacco lawyers, Wall Street lobbyists, Saddam Hussein handshakers, anyone ever involved with Ralph Reed, anyone to ever shake the hand of a crooked preacher, and so on. A politician associates with thieves and crooks and murders because he or she chooses to; a defense lawyer does it because the Constitution requires it of us all.