Football fans are weirdos.
You don't need to like him. You just need to either rate (or not) his performances on the football pitch.
You don't know him, you are unlikely to ever meet or interact with him so his actual personality beyond its direct effect upon his footballing performances is totally irrelevant.
Only if all you care about is performance and results. For me, an important part of supporting my club is feeling a connection with the manager and players, and that's easier if there's something about them that makes you like them as a person. And it's why I currently feel less attached to the team, because I've always thought Mourinho is the biggest dingdonghead in football.