Some years ago I had to resort to lawyer to right a wrong that had been done to me. The lawyer explained to me that if I expected to win my case in a courtroom, I would have to stop being angry.
It didn't matter that I was right and the other guy was wrong - egregiously, obviously wrong. It didn't matter that the facts and the law were on my side. It didn't matter that it was a serious situation - literally a life-time's worth of earnings.
As my lawyer explained, juries don't like angry people. If you go in angry, you lose.
To win over a jury of uninterested, uneducated people who don't know you requires that you be the victim. Avenging angels are presumed capable of taking care of themselves. People who shout and yell have an agenda. People who are vindictive are surely just out for revenge.
in short, people who are angry are assumed to lie.
If you claim the other guy is evil, people will automatically dismiss you because it is an extreme claim, and only activists make extreme claims. The mere fact that the other guy is actually evil does not matter, because the people you are talking to do not know the facts. If they did, you wouldn't have to say anything. The whole reason you are talking to them is to educate them on the facts. So you have to say it in a way they can hear it.
Every progressive in this country knows that the Republicans have completely sold out to the plutocrats. As an American living overseas, I can tell you that pretty much everyone else in the world has figured it out, too. But the American people - the same people who believe in creationism, ghosts, astrology, aliens, American Idol, and all those other absurdities - have not figured it out.
Until they do, all Obama can do is remain civil, regardless of the provocation. True, the Republicans scream all the time - but they're not trying to win over the middle. They got the middle by default, because the economy sucks, and people wanted change. They don't know this, though, and they are currently screaming themselves right out of relevance. Just look at Wisconsin.
Obama isn't just a politician. He's a lawyer. He's not there to whip up the base and make us feel good about our convictions (even while our policies fail). He's there to win, and he's doing it the only way he knows how.
Maybe you think his strategy is wrong; that's your right. But it's his right (and duty) to use the best strategy he knows. The least he deserves is to not have his strategy mistaken for his principles.