Snowflake Royal I've just rewatched the highlights because of this argument and I can't say I think there's much the ref got bang on.
Fox - could easily have seen a straight red
Richards - slightly more control but a worse challenge, couldn't complain at red
Murphy - a straight red, looks like intent and worse than Darikwa's
Fox - obviously they don't show the whole melee, but the bit they do show he's trying to restrain people but someone else piles in near him aggressively... Makes me wonder about mistaken identity... that's just the highlights tho, maybe something is missing.
Darikwa - doesn't look too bad to me, off the ground but both feet seem to go wide of Loader who he seems to catch with the flat of his leg, looks less bad than either Richards or Fox's to me.
The bit I've seen shows Fox placing both hands on someone's (Moore?) chest and shoving him, all done right in front of ref. Second yellow at the very least all day long.
The others are subjective and whilst I'm no apologist for referees, he sees it once, in real time and has to make an immediate judgement on seriousness and intent.