The issue for me is not that he will be biased or cheat but there is a good chance he will make a mistake and this is manifestly unfair on him, never mind City. Imagine he misses an offside. If it's for City he'd be accused of trying to show he wasn't biased and if against City, well we know how that would look.
I'd be amazed if he is not taken off this game considering he was taken off the 2008 play off semi final between Palace and Bristol City. The press highlighted the story and he was removed, although the Bristol City manager (Gary Johnson) said he wasn't bothered.