Kane opened the scoring in the 50th minute before Lucas Moura completed an outstanding brace to see off the Red Devils. Mourinho asked before holding up three fingers.
United initially showed promise in an even first half with Brazilian Fred finding plenty of space they and should have taken the lead through Romelu Lukaku after he was presented with a gift of a back-pass from Danny Rose.
Mourinho, 55, has come under fire in recent weeks, not only for his team's mediocre start to the season - including a 3-2 defeat at Brighton & Hove Albion on August 19 - but also for a number of reported fallouts with the club hierarchy and key players.
Likely fed up with rumors and recent results, Mourinho demanded respect despite his club's 1-0-2 record to begin the season. "Me three, them two", he said.
Three goals conceded: the same as in the last game at Brighton (another defeat) so nobody was doing a mental calculation of Mourinho's Premier League title haul as he turned on his heels and left the media room. That also means three Premiership (titles) and I won more Premiership alone than the other 19 managers together.
"I think for every single manager that is younger than him, he was the inspirational manager", Pochettino said.
The problem? Those three titles were won at Chelsea.
It looks like come January, Mourinho will be looking for new players. We know the end of the season is too far away, we need to keep pushing, trying to be consistent. But the words and messages coming from Mourinho do not suggest he knows which direction he and his team are heading.
"It is a massive victory for us and I am very proud of the performance", said Pochettino.
"I accept these are different times and I accept the difficulties and challenges, but my honest view as I stand here now is that Ed Woodward gave him a contract last season".
"The team was playing to change the result, creating enough for that". He needs to find a way to get himself and his team out of their downward spiral, but talking about the past isn't the way do it.