United fans are angry at him anyway because he hasn't lived up to their expectations, but if he moves to the light blue side of the city, he could become one of the most hated players among Red Devils fans.
Pogba's disappointing spell at United would mean nothing if he moves to City, cause that is where the attention will shift to for United fans, they would consider it unacceptable if one of their own goes over to their crossroad rivals, i know it has happened quite a few times in the past, but such players are always greeted with hate/animosity by fans of their former club, and that is what Pogba would face should this happen, it could even go as far as him receiving threats from a few United fans.
Having said that, this is just rumor for now, i see no reason why City would want to sign Pogba, they have enough midfielders for now, and there seem to be no need to add another to their payroll. What City need now is a world class striker and maybe fullbacks, cause they look short in that position. Other than that i do not see any need for new additions.