This is entirely true. It's also the reason that more and more extreme ideas flourish.

The disingenuous engagement disillusions more reasonable people. People left of center see how Barack Obama was treated for the mildest of progressive ideas, and then decide that there's no point playing nice. I'm sure there is a similar analogy for conservatives.

If you don't listen to reasonable, accommodating people, don't be surprised that you are selecting for people on the extremes.