Just wait till he starts performing badly and that damages the team. Even Virat Kohli was criticized for a lot of things that he had done outside of cricket. And he had also faced a lot of criticism for not being able to perform for a long period of time. I don't think the case of MS Dhoni is going to be any different.
Wrong again. MSD did mess up in the past and many fans criticized him and the Indian team badly, but that was a long time ago. He achieved some insane stuff since then which is why he is regarded as one of the greatest captains in this sport.
This is why the majority wouldn't criticize him even if he performs badly anymore(Duck in the final etc). Think hard!