I've met quite a few west ham fans who follow the filth - particularly recently which has been weird. I've had quite a significant amount of work done on my house in recent months and I've had tradesmen in from all over the place, and during that time I met 4 separate west ham fans who have been in doing work for me, all of whom favour the scum.
I also work with a ST holder who favours them, and personally know another guy who is married to a scottish girl (who has no interest in football, nor does her family) and he loves going to scum matches when he is in glasgow.
In all my many years of living in London, I have met 2 English people who actively follow and support Rangers - and that includes my time as a season ticket holder at stamford bridge. Perhaps I have just been unlucky.