#2 The brand of football
You've heard it a million times, but this is what United fans hate the most about Mourinho - the brand of football his teams produce. That kind of football is acceptable at a club like Chelsea, as they are all about winning without being too bothered about the way they win.
But for a club like United, winning is not enough - at least not for the fans. The team must win in a certain style as the fans expect the team to be trend-setters.
For a manager who has spent the best part of £300 million playing that kind of football at a club like Manchester United is less than desirable. What frustrates a lot of people is that Mourinho doesn't trust his players in offense.
In the Manchester Derby, United attacked in the second half and scored 3 goals. At the Emirates the Red Devils attacked for 15 minutes and scored 2 goals. Against Liverpool United attacked for a short while and scored twice.
So you can see why United fans get annoyed. The team has the talent and ability to play offensive football, but the manager does not allow it.