It should be about intent nothing else.
It can never be just about intent, players must exercise caution in their play with regard to their opponents safety. Always.
No "intent" because Nani didn't see Areboa is no excuse, he should certainly should have seen him or at least have been aware of his impending arrival. Nani was reckless = yellow card. Did it involve "excessive force", probably not. But IMO he was past a yellow card but not warranting a red, into a grey area and personal interpretation! What did Nani do? Immediately jump up, show his hands in apology and check on his opponent's health? No. He tried to con the referee, did this provide the opportunity for the ref to send him off?
After profiting, for so many years, from a disproportionate amount of contentious decisions at OT, seeing Nani sent off and Fergie bounding down the steps in a fury made me laugh out loud, it was very funny.
In Gijon, there is a famous song sung with gusto by Sporting fans,
"Asi asi gana el Madrid", it means (more or less)
"Yep, that's how Madrid always win", via the ref really, just like Man U. So what's the big deal?