Shinzen Young, who I normally don't follow, has some profound things to say here (HT: C4Chaos). And I think they kind of relate to the whole issue of right speech and the recent violence in Tuscon.
Of course everything's interrelated, and - to reiterate - to pretend that they are all isolated is to oppose reality.
So when Barbara says, "So, from a Buddhist perspective, we are all responsible. There is no one on the planet who is not responsible" that does indeed mean all - it doesn't mean we're all guilty of murder, but we might be guilty of being overly dogmatic in our speech to the point where the speech becomes incendiary.
The process that Shinzen describes in the video link above I think applies to the issue of right speech and dealing with incendiary speech: if our speech is at first divisive exclusionary we will create more division and exclusion; if we accept an other person's divisive and exclusionary speech as though the division exists, then we further that division.
These divisions transcend left/right politics; "a pox on both your houses" is still missing the mark by a light year.
There's a way to speak past the division.
This is what it means to "practice Zen off the cushion." It means to speak with a fundamentalist extremist from a place where the ideological gulf may be transcended. And no, this is not airy-fairy crap. This is how we're going to survive as a species until the sun starts to give out, if we have any chance at all.