My favourite part is that all of this happened in my city.
There's nothing even remotely odd about a Calgarian asking a stranger if they've been to the Stampede -- even weeks after it's ended. People here are often very friendly and open with strangers. I've had several random people at the bus stop, etc. ask me if I attended the Stampede this summer. Granted, I wasn't present during the incident, so it's possible that they were behaving creepily or trying to pick a fight, but I have a really hard time believing that the situation presented any significant danger to this guy and his wife, much less that it would require a weapon. It's Nose Hill in broad daylight, for Christ's sake, not 4plex row in Forest Lawn or the 7th/8th Macs at 3am.
Edit (from his letter):
I quickly moved between these two and my wife, replying, "Gentle-men, I have no need to talk with you, goodbye." They looked bewildered, and we then walked past them.
They looked bewildered because you were acting like a douche.
Anyone interested in seeing some of the responses people sent in from my local paper? They're delightfully snarky.