I do think, however (and I know I'm biased), that Republicans tend to be more open to honest debate than Democrats. And this gets us into trouble.
Republicans have actual plans, ideas, and philosophies. We have principles. We also have some confidence in these things. So, we trot them out, and even if they aren't perfect, they are at least superior to the non-ideas of the Democrats. Then, during a debate, if a Democrat points out a flaw, a Republican might possibly (in a moment of civility) shrug and say, "You have a valid point there." At which moment the Democrat will clap their hands and shout, "He admits his whole plan is a ploy to win tax breaks for the rich!!" and the host of the show will nod sagely and say, "These Republican talking points that you're trying to pass off as the truth, do they originate with Karl Rove?"
The other side is when the Democrats mock Bush for believing he has been Perfect and without sin for the entire adminsitration. "C'mon!", they say. "Won't you admit to making ANY errors at ALL??" And if a Republican concedes that perhaps something didn't go quite right, then -- again -- the Democrat will clap their hands and shout "Even HE admits the fact that the whole thing has been a a debacle from the beginning!!"
I think your overall point is that honest debate no longer exists on TV. I think that's true. I think that both parties are culpable, but I think the Democrats are to blame for setting a tone which makes civility a self-defeating exercise.