All troops need to be out of Afghanistan. It is clear that the locals do not want or need Canadian, American, or English help anymore. It should not be the job of the NATO nations to police the world. The original objective (to kill Bin Laden) has long since been achieved.
As a member of NATO, Canada is responsible for sending troops to Afghanistan. Canada is an important ally of the United States, and they need to lend their support to their efforts in the War on Terror. It is only with strong international support that terrorism can be stopped in the future.