As a Brit watching this spat from across the Atlantic, I can't see why anyone has a problem with Kendall carrying a firearm. He's clearly trained in its use and is a responsible and thoughtful former law enforcement officer.
Many Brits, especially in central London, would be surprised if they knew how many people around them were armed. With the current terrorism alert, virtually every officer of SO8, SO13 and SO19 (Special Branch, Anti-Terrorist and Firearms branches) is deployed on the streets, many of them in plain clothes. But most people have no problem with that.
Unfortunately our firearms laws have become so draconian that pistol-shooting looks like dying out as a sport over here - pace this very good piece by Labour MP Kate Hoey (who's from an Irish hunting family and is a damned good MP). And it mentions Christmas!
But much anti-gun reaction is from those who have never had anything to do with them (and I know that the Snowdrop campaign, set up in the wake of Dunblane and which led directly to the current firearms law was a reaction, but it was quickly taken up and taken over by those who had nothing to do with the tragedy and who had their own agendas to further). Personally, I find knives much more scary when in the wrong hands.