Well good, since professional and volunteer firefighters are the most common arsonists. People with violent criminal records should not be in those fields at all.
Your article cites 100 annual firefighter convictions for arson in North America. For your claim to be true, that means fewer than 200 arson convictions annually in all of Canada, US, and Mexico. It says firefighter arson is common, but does not appear to claim that they are the most common offender.
