I think both are true for different factions of the fan base, but with that said, I think the criticisms of certain foreign players are much more personal and vitriolic. The character assassinations I see for Pogba and Martial in particular are plastered in every thread you go into on this forum, usually unprovoked. Foreign players, particularly, of African heritage are routinely referred to as lazy, arrogant and thick, and whilst I don't think all of the people saying these things are prejudiced, I can't help but think that if they weren't black and French, people wouldn't buy into it as easily.
With Rashford, although some of the takes are horrendous, I rarely see such personal attacks, even though I know some have started to use his off-field work as a stick to beat him with.