Complain about attack ads if you like, but we're only debating them because we deserve them.

Last week we were once again exposed to attack ads in Canadian politics. The Conservatives welcomed Justin Trudeau as the new Liberal leader by suggesting he was in over his head. Their attack ad included a bunch of out-of-context quotes and footage of Mr. Trudeau taking off his shirt in strip-tease format (the footage came from a Liver Foundation fundraiser) with carnival music in the background. The charity was the immediate beneficiary of the attention—the original event raised less than $2,000 while in just two days last week, more than $10,000 of unsolicited donations were sent the Liver Foundation's way.

The public seemed turned off; the columnists had lots of fodder; and the TV stations earned some ad revenue. Both the Liberal and Conservative operatives claimed victory at the end of week one in the "define Justin" debate. (I prefer the verdict of one battle-hardened political vet who noted that picking winners at this stage is naïve and premature.)

There was plenty of sanctimony thrown into the discourse with some misguided editorialists equating these ads to bullying. Mr. Trudeau used the occasion to brand himself as positive and high-minded, promising not to respond in kind. Similar promises have been previously made and abandoned. The critics who demonize sloganized simplistic ads as a persona of the Harper Conservatives clearly have short memories. Neither were they paying attention to another negative ad campaign launched last week by the Public Service Alliance of Canada against the Harper government's environmental policies. It makes the Trudeau ad seems like child's play, although it has garnered minimal media attention.

Does this kind of free speech matter? Is it worth defending?

In the midst of the muddle, a few points need to be made. The reason we see so many attack ads and branding messages from our political leaders is because they work. The reason they work is the public's short attention and shallow engagement with politics. An electorate taking politics seriously would stop being swayed so easily by mere branding campaigns—positive or negative.

Secondly, in the mix of factors that determine political decision-making, attack ads might provide a public service in proposing a narrative that may in fact be true. Andrew Coyne rightly pointed out that not all attack ads work. The difference between the ones that work and don't work is when the ad proposes a narrative that in fact has credibility and the targets behaviours fit within that narrative. When the target of an attack acts true to type, the ads have leverage. The power of the ad is to propose a narrative within which the targets behaviours can be consistently interpreted. To an audience which only reads headlines and follows politics superficially, reinforcing such a narrative is a much easier challenge than persuading an audience ready to listen and consider the nuance of behaviours and arguments.

Those who find attack politics distasteful often cite these as further justification for their disengagement from politics. They complain about politicians' behaviour while using it to justify their own cynicism and complacency. Perhaps the antidote to attack politics is paying more attention—so that simplistic branding messages, when they are untrue, motivate us to punish leaders who tell lies.