Amid speculation that the former Chelsea and Real Madrid boss would be sacked regardless of the outcome of the visit of Newcastle, United showed renewed heart as they recovered from a first-half deficit.
Kenedy and Yoshi Muto's goals put Rafael Benitez's side 2-0 ahead at the break, but Juan Mata, Anthony Martial and a 90th minute Alexis Sanchez header turned the game around.
It remains to be seen whether the victory - United's first at Old Trafford since the opening weekend of the campaign - will be enough to save Mourinho from the sack.
If indeed the Portuguese coach does depart he has ensured he has gone out swinging, claiming the media have orchestrated a campaign of "wickedness".
"As a friend of mine was saying to me this morning: if tomorrow it is raining in London it is my fault," he told BT Sport after the 3-2 success.
"If there is some difficulty to have the agreement of Brexit, it is my fault. And I have to be ready for this.
"I think a lot of wickedness and a clear man-hunting which I think in football is too much.
"It is a life I love, it is the life I worked for since I was a kid and I will love this until my last day. It is one more thing in my life."
Such has been the viciousness of the criticism, according to Mourinho, it has affected the mentality of his own players.
Mourinho identified Marcus Rashford, who was taken off mid-way through the second half, and Scott McTominay - a half-time replacement - as players who have struggled amid the increased scrutiny
"I am 55 years old and spite of this, this is the first time in football I see a manhunt," he added.
"I can cope with it and I can live with it. I think some of the boys, they are not the man that is hunted, they are not coping well with it.
"Some of boys, Marcus Rashford was sad on the pitch, Scott McTominay was scared on the pitch. Even all the players commit mistakes that are not normal."