A Lesson in Logic
Long ago and far away, my undergraduate major -- one of them, at least -- was Philosophy. Based on having watched too much Star Trek, I took a course in logic. Now, on Star Trek, Spock's logic was basically a sort of inchoate Stoicism with a lot of "I like what will make the next gag work", but as I was exposed to real logic, I was hooked. Eventually that led me to mathematical logic, which turned computer programming from a handy job I was good at into an intellectual obsession, which made me the cranky old hermit I am today -- but that's another story.
But my first Philosophy course was on Rhetoric and Logic, and that was what made me change my major. There were actual rules for arguments, and they were rules that had clear reasons behind them. Even better, there was a catalogue of common flawed arguments, or fallacies, and seeing those rules made it easier to pick out flawed arguments.
For me, it was a life-changing experience. (Don't judge.)
One of those fallacies has been much bandied about this week. The classical name for it is tu quoque, which is the Latin for "and you're another." (Really.) The problem is, people are misusing it.
Here's a paraphrase of an argument I've seen over and over again, all week, on the Rush Limbaugh thing.
"We shouldn't bring up the things liberal talkers say about conservative women. What Rush said was indefensible and anyway, just because they say it doesn't make it right for us to say it."
Sometimes people explicitly call out the tu quoque making this argument, but in any case the point is to claim it's tu quoque to defend Rush by pointing out the offenses of the liberal talkers. The flaw is that tu quoque is to claim "It's okay that I did this Bad Thing, because those others were doing it too." However, I don't know of anyone who's defending Rush calling Fluke a slut -- not even Rush.
Saying "If it's bad when someone on our side does it, then it's bad when someone on the other side does it too" is perfectly valid -- and very unpopular.