Why would anybody, United fan or otherwise, question that assist? He plays the ball, gets a touch on it, and he's looking at James when he does it. To be honest I've not seen the exchange where people are questioning it, however I interpret it as part of the super negative 'fan' that loves to hate the management in particular but also like to overstate every minor issue with a player. I.e. Maguire, AWB, Fred, James, Rashford, Ole, the tea lady, the list goes on.
Martial gets a bashing by me because he's a lazy cnut who doesn't care enough about the badge to even run in it, never mind being shite in front of goal, the least you do is run. He's the antitheses of Bruno.
Why anybody would question the assist and argue that he doesn't deserve an assist for ensuring the ball (that was about to be cleared) gets to James is beyond me.