I found another article with more details on Ignatieff's Afghanistan argument. As reported on the CBC, the rationale he brought forward for voting for the Afghanistan extension comes down to supporting the troops.
As I see it, the Canadian Armed Forces are a resource of the Canadian nation and the government has a responsibility to apply this resource wisely in our national interest.
"Supporting the troops" is a valid idea, but it applies to moral and material support for the soldiers and their duty, as well as the proper degree of respect. It is entirely independent of whether or not a particular mission should be extended.
In a later interview Ignatieff gives some real reasons for supporting the Afghanistan extension. So, he certainly may have a valid reason himself.
However, to drag out the "support the troops" line is a pathetic attempt at using patriotic vapour in lieu of an actual argument. We don't need that in Canada, and I regret that it's also the style of our sitting Prime Minister.