Suppose its the problem with the rules, it's interpretation. For me all three should be red, but i wonder whether you start to introduce an orange? 10 mins in the bin but that player can't return to field of play and must be replaced by a sub?
In porter's case, it was always high and he's a short lad and even if he had been standing upright completely, it looks like still head contact.
The problem is there are a few refs shooting from the hip but also players are getting around the rules in most plays, i see that attempted neck rolling has pretty much dropped off the face of the earth unless it's conceding a try and a number of french and irish teams tend to clear out pretty recklessly.
I know you can't always manage these but i think sometimes the refs are given so much to keep an eye on that it's actually to the detriment of the game.