Ask your liberal debate buddies if they have seen Farenheit 911?
If they have, they would have heard Michael Moore himself say that Canada is loaded with guns. The difference is that the culture of Canada is not particularly violent. Their TV news doesn't have crime, crime, crime, crime on at 24 hours per day.
What Mikey glanced at but refused to analyze was that of race and urbanization.
Remember when he asked the producer of COPS (a self-described liberal) why he kept showing urban black guy after urban black guy getting roused, tackled, pepper sprayed and hand cuffed by cops night after night. The liberal producer was embarrassed when confronted with this, but he had to say that his job was to capture energetic police interactions and these happened to be in the ghetto, not on Wall Street.
If you remove the black inner city crime rate from the American mix, America looks a lot like Canada. In fact, rural blacks are much more commonly armed than their urban counterparts but are no more violent than rural whites.
The City. It makes ya crazy. Or, secondarily, dense urban populations lead to anonymity while increasing the chance of encounter with a potential victim.
Look at the case rates by population density for communicable diseases such as TB and HIV. Lots of chances to interact.
You'll find this with a few web searches. In the meantime, throw the above at your debate partners.
Rick