In this part of my life( in this age i mean) i know that all players are "mercenaries". They want money and titles. We can love some players, their passion, quality, etc... but in the end, they are all mercenaries. Rashford is a Manc, "born and bred" but he will want to go also if better offer comes. It is simple. And i don't have any problems with that. That is modern football.
It is on clubs to beat other clubs for keeping/buying world class players. Sounds harsh and we all can say phrases "feck him, this is Man Utd" but if we want to keep Pogba we must give him new huge contract and squad with which he can win titles. It is reality. He is one of those players who can choose club. He is not Jones or Fred or Smalling or Lingard who must fight to be in this club because it is career high for them. They can only go down regarding money and club reputation.
As i said, approach "we are Man Utd, it is honour to play here", is not valid anymore. So, Pogba is a must have player for us and we must do everything to keep him here. Or we can be proud, sell him and be Arsenal. Club without titles that have goal to be in top4.