Right, this attitude can fuck off.
There are no rules to which football team you support, and nobody's being a gatekeeper about who can and can't support ours.
There's nothing wrong with supporting any team; what's annoying is when people who have picked a team because it wins every week then starts giving it the large one to die-hard supporters of other teams. That can fuck off. But some kid in Thailand or Canada with a love for Manchester United? Sound, I hope that they enjoy their support, in whatever form it takes.
And this kid supports Coventry City; he's hardly a glory grabber, is he.