A silly debate that never disappears from the political scene is whether "attack ads" should be allowed.
Aside from the free speech component of the matter that make attack ads constitutionally protected, the motives of people opposed to them is rather transparent. It's because the candidates they support are vulnerable to them. The previous two Liberal leaders were particularly harmed by attack ads in Canada's last two national elections.
Stephane Dion was the target of a very effective Conservative ad campaign leading up to the 2008 election that portrayed him as "not up to the job" of being a leader. Michael Ignatieff was similarly harmed in the 2011 election by being successfully characterized as an elitist who was "just visiting" Canada for the sake of personal ambition.
The raucous nature of political campaigns are really about pointing out not just the advantages of one side, but the deficits of the other. This relatively minor test of fire is an important element of the election process for a very basic and obvious reason. If a candidate who wants to lead a country is incapable of dealing with an attack ad from a fairly benign domestic political rival, how could they possibly function as a leader on the world stage, dealing with potentially hostile foreign interests?
In that sense, attack ads are the most basic test someone who wants to be put in a position of power and responsibility should be able to overcome. If they can't, they have no busness asking millions of Canadians to entrust them with that responsibility.