As I understood it VAR was only for "clear and obvious errors", has that mandate changed? Because truthfully there was no clear and obvious error in the initial yellow card and Mike Dean as the VAR overstepped, on that basis I think Saints should appeal it and point out all the previous incidents with Mike Dean. Sure in slow-motion at the side of the pitch in an emotional atmosphere, yes I can see why the on-pitch referee gave a red but it shouldn't have come to that point in the first place.
The PL has to make its mind up, is VAR allowed to second judge all on-pitch referee calls in slow motion or only the "clear and obvious", and define what that means. Sure if the on-pitch referee cannot see something, or the action is too fast and or can be objectively measured (goal line, maybe offside) then sure, but when the referee has a clear view and makes a call in real-time, then no, forget it.