Some people have action jobs where they have firearms pointed at them on the regular. Very quickly you learn that there is a world of difference between having a well made and maintained firearm pointed at you by a trained and disciplined professional, and having some incompetent moron waving a gun of unknown status around randomly and getting swept with the muzzle.
For all you guys getting your hackles up about snipers on the roof at parliament hill, you should know that there have been snipers on the roof for just about every mass gathering in Ottawa's history since at least 9/11.
I can't think of a time in Canada's history where a law enforcement sniper was involved in a wrongful shooting. Don't fear the police snipers. Be more concerned with not standing beside the guy who is there to cause trouble.