Mangala showed how poor he was on a very regular basis at City. Negative fan reaction was understandable and, in my opinion, usually well deserved. He simply isn't/wasn't a good footballer.
Bravo had a horrendous start at City and looked like he couldn't save anything on target. Again, negative fan reaction was understandable, but (again imo) perhaps unfair. Pep threw him in and let him struggle... Seemingly, just to show Joe Hart that he was out of the picture. This was the poorest piece of management I'd seen from Pep in his time at City.
Until...
Kalvin Phillips hasn't even had a decent chance to prove or improve his performance. He's been left high and dry by Pep and fans - no doubt hanging onto and influenced by Pep's every thought - jumped straight on his back. Pep's (seemingly obvious) lack of faith in Kalvin Phillips does no more than increase 'fan hatred' of the lad.
I'm no great believer in Kalvin's ability to play at elite level, but I do believe that he should be at least given a chance to show that he can do a job at City. He certainly doesn't deserve the level of criticism aimed at him. It's got out of hand.