That's strange; I thought they were just supposed to give directions, not spout unimaginative bullshit. Must have been programmed by a bitter City fan or something - I hope you both kept your reciepts.
I suggest when you get your replacement sat-navs, you take a trip up to Manchester. You can walk through the city counting the number of people you see in United shirts and compare them to the number of people wearing any other football shirts. When you've realized how ridiculous your assumptions are, take yourself for a look around the Old Trafford museum. If you get there early on in the day, you might be lucky enough to see the Premier League trophy being polished.