The Blind Side, the movie that gave Sandra Bullock her best actress Oscar, which captures the extent of the blue-red divi' />

There's a memorable line in The Blind Side, the movie that gave Sandra Bullock her best actress Oscar, which captures the extent of the blue-red divide in American society.

The movie is based on the true story of a rich, white, conservative Southern couple who adopt a homeless black boy. When they hire a teacher to help him catch up, the teacher confesses to them her dark secret: she's a Democrat.

The husband remarks later, "Who'd have thought that we'd have a black son before we had a Democrat in the house?"

Barack Obama was supposed to be The One who would transcend that kind of dyed-in-the-wool partisanship.

He was supposed to be the post-partisan President (as well the post-racial one; good luck to that), a beacon of reasonableness and common sense whose rousing rhetoric would overcome the rancour and toxicity of old-style politics, and help divided Americans find common ground.

Well, that was the plan, anyway. But look where it got him. Deserted by a disillusioned left, and well and truly shellacked in the midterm elections.

What went wrong? The New Republic's Sean Wilentz posits that Obama is the victim of the "socialised personal movement" that propelled him to power. The movement was based on "values, emotions, feelings", rather than "any particular policies or political goals".

Thus, he argues, its followers were blind to the reality of democratic government, and destined to be disappointed.

As Bill Clinton found after his first two years in the job, "oratorical force" doesn't triumph over "grubby politics"; a President must be prepared to engage in "day-to-day political trench warfare".

Indeed, Wilentz writes, "the grind of political infighting and compromise must always have priority. It could well be that Obama's survival as an effective political force for the next two years and his prospect for re-election - and any viable future for social movements - will require engaging cleverly and doggedly in what his movement theorists derided as status quo politics."

It's not only the notion of bipartisanship that's taken a hit but also the idea that reasonableness and civility can win out over a recalcitrant Republican class determined to see Obama fail.

Worries about incivility and partisanship are a recurring theme in American politics, according to my favourite Harvard philosopher Michael Sandel.

He writes that Americans are right to worry about the erosion of civility in everyday life, but that in politics, "civility is an overrated virtue".

"The problem with civility is the very thing that tempts politicians to extol it: it is uncontroversial.

"But democratic politics, properly conducted, is filled with controversy. We elect politicians to debate hotly contested public questions - for example, how much to spend on education and defence and care for the poor, how to punish crime, whether to permit abortion. We should not recoil at the clamour and contention that result; it is the sound and spectacle of democracy."

Still, the dream dies hard. Even as Obama was about to be humbled, The Daily Show's Jon Stewart and fellow satirist Stephen Colbert were organising a Washington rally ("To Restore Sanity And/Or Fear"), and urging Americans to "take it down a notch".

Stewart criticised the increasingly shrill rhetoric coming from both left and right wings. (That earned him criticism for "false equivalency" from the left, which argued that the lies told by the deranged right - for example, that Obama is a Muslim and foreign-born - were far worse than anything the nutty far left might have said.)

Like Stewart, I've yearned for more civility in political discourse, but I'm wondering now if that is a forlorn, even misguided hope.

Polite, rational debate isn't always what's called for. After an old friend of my nephew's described a run-in that he and his mates had had with a group of Polynesians on his Facebook page, one of the commenters made sweeping statements about violent Polynesians, yet his blatant racism went unremarked and unrebuked until my nephew joined the conversation.

My nephew called him out in unequivocal and impolite terms that shocked me on first reading, but seemed entirely proportionate on reflection.

We've become too tolerant of racists.

Last week, an Invercargill primary school principal got nationwide publicity, courtesy of a couple of right-wing bloggers, for comments she'd made on her Facebook page about Education Minister Anne Tolley. She'd characterised Tolley's tactics on National Standards as Hitlerian.

These days, everybody has an opinion and a Facebook page on which to express it.

Politics is rude, raucous and sometimes noxious. And maybe it has to be. Better a loud, even rancorous, war of ideas than quiet surrender.