I suspect there are various reasons: 1) the one you cite: let's all hate what the majority likes (which is an assumption), 2) because of the 'Murica-centered patriotism that has been abundant in a lot of COD titles afaik, 3) COD is what kids play and I'm a grown-up. I'm sure more would come to mind if I could be bothered to think more about it.

But anyway, I have fond memories of the first COD+expansions. I think I stopped playing the franchise after MW2, due to lack of interest, and stopped playing MP-shooters due to becoming too slow. Age takes it's toll on the hand-eye-coordination...