Oh you thought they were polite to each other? Martin stared straight at the camera instead of his opponents; Layton kept interrupting other's speech; Harper used an extremely intimidating tone when he challenged Martin regarding some issues; Duceppe, ah nobody cared about what he wanted to say in an English debate.
Unlike Canada, US presidential debate is actually not a debate, they don't talk to each other, but to the moderator. I've watched all 3 presidential debates between Bush and Gore 4 years ago, I'd much prefer that format: for one thing, I can actually hear their agenda.