Stubborn Ignorance or Dishonesty?

I've been thinking a lot lately about political dialogue, and specifically where to draw the line when choosing to engage. 

It seems reasonable that in order to have an honest debate, the opponent needs to either, A) Understand the legitimate premise of your viewpoint, or, B) Admit that they don't and thus make a good faith attempt at understanding why you believe what you believe.  Only then can we critique one another's assumptions and present opposing opinions.

So, an absurdly popular right wing argument right now is that Democratic spending is out of control (mainly TARP & ARRA), with no mention of either the Keynesian or emergency basis to either plan.  The idea is simply an extension of the usual conservative opposition to government social spending, as if the financial crisis never happened, as if the bank bailout wasn't an emergency attempt to shore up an imminently collapsing banking system, as if the stimulus wasn't entirely based on Keynesian economic assumptions.

So one either knows these things or one doesn't.  To not mention them is then either ignorant or plainly intellectually dishonest.  At this point, the vast majority of conservative commentary I hear falls squarely into one or the other camp.  The real wackos seem to just be ignorant - which would explain much of their vitriol.  (Glenn Beck at CPAC today argued that failure would have been a good thing because we need the "freedom to fail" in order to learn to do what is right.  How his self-help gobbledy-gook applies to an over-leveraged financial market upon which our entire economy hangs in the balance is beyond me.) But the more calm and reasonable figures I'm guessing are just being dishonest.

If Keynes was right, then the stimulus was too small if anything, according to what his model predicts.  If he was wrong, then by all means explain to the mainstream of economists that has generally accepted his theories.  If bailing out the banks was a bad idea, explain why doing nothing would have been the better option - when most estimates also widely agree that a domino effect would have brought our economy) if not the world's) to its knees? 

Why waste time with someone who is either being dishonest or won't take the time to try and understand where you are coming from?