Why are you ignoring posts which prove you wrong to then start arguments with other posters?
The closest has been the stuff ESPN reported, which makes me understand why it was given, but just highlights how stupid the whole system is.
By the letter of the law, it isn't a red card. You're not going to change my mind on that.
By the largely secret, extra guidance, that only the referees know about (unless someone bothers to share it with the media), I guess it sort of is. But that guidance is demonstrably stupid as an ankle can buckle without contact and a more forceful impact than Rashford's won't buckle it if the angle is slightly different.
Serious foul play is surely not there to punish players with dismissals and suspensions for accidental injuries (in this instance, an injury so minor the player didn't even have to come off) caused by perfectly normal movements? If it was, surely the actual law would be amended to reflect such?
A lot of the "definite red arguments" haven't even referenced the guidance, and instead either refer to it being "studs up" (which it wasn't, a kick/stamp (which it wasn't), and/or a tackle (which it wasn't), or even start bringing up daft comparisons ranging from studs up slide tackles, kung-fu kicks to the face, and even throwing stones at swimmers.
I'll maybe concede that the ridiculous guidance possibly makes it a red, but the two stupid handballs were correctly called when you look at the definitions, yet nobody is going "well actually..." about them.
It can be "never a red" because the laws/guidance are not fit for purpose while actually being one because of those current laws/guidance.
I'd actually argue even then that this was not a tackle/challenge and therefore can't fall under serious foul play. Only the vagueness of the definition of challenge gets you close.
And while we're on that subject, the current protocols for pitch-side monitor VAR checks needs reviewing because it's absolutely bonkers that the first thing a referee sees is a zoomed-in, freeze-frame of the worst angle of the incident, and not a real-time replay from which he can request different angles/speeds/levels of zoom.