It's hard to judge this topic without logger and ElfGrinder2k participating. You do want the opinions of the professionals, after all.
The bottom line, to me, is whether we consider use of an informal fallacy to really negate the point being made by the person using it.
If we hem in the discussion of the latest outrage on the left or right to the actual facts and elements surrounding the particular action or statement, then sure... a Tu Quoque loses the formal debate.
But since these discussions are not "formal debates", I don't really think I'm giving gotcha points to either side when they point out that the person crying glennbeck tears has ignored similar actions, or actually supported them, when performed on their own side of the aisle. I'll see your "waaaah that's a tu quoque fallacy" and raise you "Objection over-ruled. I agree with the plaintiff, it goes to credibility of the witness."
It's used around here (by both sides... I repeat) like bigots use the race-card-card. It's to disarm your opponent by shouting "Tu Quoque, I Win!" It's sort of like Mornington Crescent for Skeptics.
And we see both sides use it in the same debate.
"Oh, yeah.... where were your complaints when Walker was doing it; you seem very concerned that Hillary is?"
"I'm rubber and you're glue. Where was your defense of Cheney, Walker and Powell. Only when it's a Lib, LOL?!"
Either admit that we're arguing for the partisan side or take a thinking-person's approach to these questions. It's no saner or more supportable for Paula Progressive to use campaign contributions to landscape her house than it is for Carolyn Conservative. If you split hairs on the finer points and the amounts of the corruption, you're probably a partisan. If you view the cases in detail and come down with variations of culpability according to the actual facts, then call yourself a critical thinker or skeptic, at least for that instance.
One poster in this thread has overtly demonstrated that objectivity. Happens to be a poster normally tagged "a conservative". Big deal. Anyone can be fair. You just have to try. Unfortunately, most of us root for our home teams and it comes out in who/what we're willing to defend/attack.