I guess, you don't know how Mourinho handles their squad. He is actually a smart person, but sometime he make a blunder and harming himself and the team. I don't know how much time he got a red card when he trained all the teams in this world. Sometimes, his strategy he used is enough effective to hold the opponent attacker to create a goal. But, because of his actions always make a point to pay attention to him, so that make a referee to be focus on him, and give him a red card in vain. On other side, MU is one unstable club, they still have problem with consolidation player, so that condition utilized him to just hold and wait on defense.
I agree with you that Mourinho must avoid red cards that are harmful for his teams only. However, I saw another fact that Jose Mourinho has become less reactive than in the past when he was a younger coach with more emotion. I want to say that even he tried to change himself, be more calm on pitch, and reduce his reactions, when he reacts, referees tend to be too strict with him.
I think you can consider how referees treat with other coaches, to see Jose Mourinho tends to receive stricter punishments in cards than other coaches. Referees tend to give less conversation, warnings to Mourinho and more likely give him a card directly.