Ummm for the love of G-d.
No one is denying the existence of left wing freakazoids or that some of them are dangerous and violent.
However, it gets old, really old, to hear them dragged out of the boogy man cellar every single time a right wing freakazoid gets brought up.
First off, even if the far left nuts were a fraction as organized, violent or broadly supported as the right wing nuts are, it would not excuse the actions of the wingnuts. The existence of Charles Manson (Left wing freak) does not mitigate the crimes of Timothy McVeigh (right wing freak, who killed many more people). If a man has his leg broken, the existence of someone else’s broken arm does not mitigate the pain he feels or help knit his bones.
It is utterly stupid to bring up. At best it is like crying mommy, but he got to steal a cookie, why can’t I?
But beyond this, let’s get real.
There are leftwing freaks. No two ways. However, there are nut enough of them to make a tea party. They do not have a major national party (the GOP) feeding them red meat, and they do not have Fox, Rush, Hannity, Beck, Coulter, Malkin, The Harpy, RSM, etc… constantly whipping them into a lather. They do not in general own guns or talk of secession. They do not believe that Jesus wants them to retake America from socialists and brown people.
So even if somehow, the existence of one bad thing could mitigate the effects of another bad thing, it is still stupid to bring up, because the right is far far worse.