Indeed, many Man United fans do not accept the referee's decision, they should blame ETH's decision, in the bigmatch match using the wrong formation and making ridiculous substitutions. Even if the referee wanted to be fair then the score would also be different because in this match Arsenal also suffered a lot from the referee's decisions, the score should have been 4-1 for Arsenal.
Fans always defend their favorite team in any way. But sometimes they do something annoying, they blame the referee for the lose. Sure, the coach should take responsibility of the lose, fans must blame Ten Hag. I also think that Man United got the defeat because of the wrong tactic used by Ten Hag, especially after normal time. So, there is nothing to do with the referee. 
I look at it from a neutral position, Arsenal deserved to win. The game was dominated, when they controlled the ball they were really scary in contrast to Man United who seemed to rely more on counter attacks. Arsenal's creativity also looks more prominent, Oddegard and Martineli are very dangerous.
Indeed. Arsenal dominated the match. Arsenal won the ball possession, they made more shots, and they played more effective during the match. Actually, Arsenal deserved to get full points in this match. Arsenal players simply played better than Man United players.