Well, the partisan reaction is predictably split:

But I think Chris Matthews lost this battle. He wouldn't have been the loser if this were a wiser, more thoughtful political culture. But we're stuck with the political culture we have.
This reminds me of office arguments I've witnessed (and participated in): if you raise your voice past a certain decibel level, the validity of what you're saying is utterly ignored. You're required to make nice, even if you have a legitimate reason for outrage. You're supposed to tug a forelock and pretend that the sleaziest person in the room is, perhaps, no disrespect intended, inadvertently a tiny bit off base on one or two points. That's the only way you're allowed to argue.
It's unfair, but Matthews needed to seem half as outraged as he was, and make his point twice as effectively as Priebus, in order to be taken seriously at all by Mika and Tom and the other civility cops on the panel. When Priebus said,
And you know what, have we really gotten to the point where we can't have any levity at all in politics? I mean, we have gotten to a place in politics that is ridiculous, and no one can say anything that is remotely humorous.Matthews should have asked: So if Barack Obama makes a joke about Mormon underwear, you're just going to shrug it off? You're going to say it's just a joke and it's OK, and you're going to go after anyone in your party who's outraged?
Near the end of clip, Matthews has a second wave of high-decibel outrage -- justifiable outrage, given the fact that Priebus played the "un-American" card himself. But under the civility rules imposed upon him, Matthews needed to give us less volume and a more effective counterargument:
PRIEBUS: But I think Obama's policies have created a sense that, for whatever reason, he's looking to guidance -- as far as health care is concerned, as far as our spending is concerned, as far as the stimulus packages are concerned, he's looking to Europe for guidance.Matthews lost it there. I don't blame him. He asked whether every president who ever followed Keynesianism was European, or every president (both Roosevelts, Truman) who ever wanted universal health coverage was European.
Good as far as it goes. But I wish he'd asked: So what about Romneycare? Did Governor Romney look to Europe for guidance?
Matthews lost this one. Alas, it wasn't a fair fight.