It's not even just about him supporting them. In plenty of other cases it's about any potential conflict of interest. Mike Dean in the example above, Kevin Friend, a Bristol City fan couldn't ref a Spurs game in 15/16 because he lived near Leicester. They're no different to Anthony Taylor's situation.
Aye, I agree with that. Just think it would have been pretty easy to prove if he was a Man Utd fan as suggested here