Sorry, it turns out you are right, it's more like a quarter: http://www.gallup.com/poll/127181/Tea-Partiers-Fairly-Mainst... Still way too many people to be tarring with a brush while claiming to be rational about disagreement.
The politics of the tea party are not my concern here. My point is that you shouldn't claim to be open to disagreement, except for that thing over there that commands the "support" of tens of millions of people. That's simply called not being open to disagreement. Honestly, that's fine; I doubt there's anybody here who is actually open to every argument you can find 25% of a country or world to agree to. Just don't pretend otherwise. As that link shows, there's no obvious "well, that's just the stupid people" argument available, either.
(I do draw the line at the "supported by millions of people", though of course I can't draw a bright shining line, because there are practical limits; one need not spend a lot of time pondering one guy's theories about the Time Cube. But dismissing entire quarters of a country at a time isn't anywhere near the line.)
By analogy, should I also not be dismissive of creationism, which fails to postulate a single verifiable claim which has not already been disproved? If I am to be rational, then I must also be able to expect at least some baseline of rationality from those I converse with.
In summary, yes, I am open to disagreement, but I'm not open to be respectful of groups which have nothing with which I can even in principle disagree.
Apparently, it wasn't a favored group of people by HN standards, because if someone had come on and said the same thing about Democrats and I had been standing up for Democrats, I guarantee I would have been upmodded to the sky. But "not the favored group of people" is exactly who you need to be listening to if you're going to be "open minded". Smacking someone down for merely suggesting that if you are open minded you shouldn't be insulting the people who disagree with you is demonstrating the very sort of poser open mindedness that I'm speaking out against.
And I choose and emphasize the word "poser" quite deliberately. Everybody knows they're supposed to say they are "open minded". Few actually do it, but everybody sure does claim it!
I suggest that your "maturity" is still perhaps not to the point where you should be lecturing others quite yet.