It's a response to not provoking an assault in my experience. Most Commonwealth countries are like this in the anecdotes I've witnessed, where brawling is common and laws lax on manslaughter. If you don't say anything you will find yourself getting beat up in broad daylight whereas other countries you can be as rude as you want without physical repercussions. Try walking into some guy in Winnipeg and brush his response off it's a provocation you want to fight where in other cultures this would be absurd.