Without dismissing Rooney's personal idiocy, I'm surprised the linesman hasn't been put under more scrutiny. The incident, being as vigorous and as wild as it was, was not only blatantly obvious from afar (which also questions Chris Foy's integrity as a referee) but it happened literally two yards from the linesman!
Why didn't he raise his flag? There's several possibilities that I can think of: 1) He thought it wasn't a foul, since there was no contact. This seems to be the general consensus in the aftermath. 2) Bias towards United players. 3) He simply missed it.
Addressing the last issue first, I invite you to watch the incident again, this time focusing on the linesman. In the video, you can see his eyes are clearly fixed on the incident at hand.
So he saw it. And ignored it. Did he conclude that it wasn't a foul, because Rooney didn't make contact? This seems to be the prevalent explanation for the linesman's inaction.
If he did, then I'd say it was the wrong conclusion.
Rooney may not have made contact with Adoulaye Faye but the intent was clearly there for all to see, and the consequences would likely have been bloody. When a player has a "high foot" or shows studs in a tackle there doesn't need to be any contact for the referee to call it a foul, because there's a high risk of injury in those sort of challenges i.e. it's dangerous play.
It should not have been any different in Rooney's case.
And whether he should've received a red card for it? Do you remember another high profile case involving Roy Keane and Alan Shearer where, again, contact was not made, but the intent and high risk of injury if contact was made, was very clear. Was it wrong to give Keane a red card because he didn't make contact?
There has been a long standing belief in football that the bigger teams, especially United, are given biased decisions from referees, especially in the big moments i.e. penalty decisions.
Personally I've never subscribed to that particular belief. Not that I think that the majority of the decisions in the past were correct; I just think that, in general, penalty decisions are not clear cut anyway. I suppose I like to assume that referees have no vested interest in the outcome of a match, and will always try to be as fair and impartial as they could possibly be.
But even I did believe that referees were being biased it's hard to discern the truth about a referee simply based on what one observe in a match. Unless decisions have been persistently wrong over a period of years, it'd be unfair to make an uninformed judgement based on one incident. However, I have to admit, coupled with the Ronaldo incident in the same match, which was also just as clear to the eye as Rooney's and also went unpunished, grants me a pertinent suspicion at the very least.
And with the Respect campaign clearly not working, the question that comes to mind is: are managers' pre and post match bullying of referees really having an impact on a their match decisions?
The more that referees have to think twice about decisions and more specifically the implications after it, the more ambivalent they'll feel, the more doubt will be cast into their mind, and in the split moment that they have to make a crucial decision, the more they'll be inclined to choose the easier, more favourable option.