Forget more civil political discourse, I'd settle for more adult discourse.
If a Republican lawmaker from a liberal state had been shot by a person of color I'd expect the more vitriolic Democrats (Keith Olbermann) to catch flack and I'd want them to man up and take the criticism like adults. That's not what happened. A Democrat was shot by an anti-government WASP so it is only natural that the Becks, Limbaughs, and Palins of the country catch some heat. And they are reacting like children.
The 'I'm Rubber Your Glue' Defense
The above link is just one of thousand of examples where Republicans respond to criticism by claiming that Democrats are being even more mean. Of course it sounds like a pathetic schoolyard whine about hurt feelings because that's what it is.
The Cooties Defense
This goes a bit further and claims that the shooter was infected by Democratic cooties and it doesn't matter what Sarah Palin said because Democratic cooties are more powerful. Part of this is the Demon Weed Sub-Defense which claims Loughner is a drugged up hippy atheist (i.e. average Democrat).
The 'What Cookie Jar' Defense
When a two year-old is caught standing over a broken cookie jar she'll go to comic lengths denying everything. Palin aide Rebecca Mansour took that stand when she claimed that Palin's famous "Cross Hairs Map" that targeted Congresswoman Giffords were really just "surveyor’s symbol." Like the two year-old, nobody believed that.
The 'Someone Else Did It' Defense
When denying doesn't work our two year-old will blame someone else - the dog, her brother, the neighbor, her imaginary friend. In this case the favorite someone else is Sheriff Clarence Dupnik who, apparently, should have preemptively arrested Loughner while surrounding Giffords with a phalanx of armed men to protect her.
The truth about who Jared Loughner was at the time of the attack will, hopefully, come with time. Until then, just grow up.