Having seen a replay of Nani's red now....I mean, I understand why it was called a red, but it's hard to say what Nani could have done differently except not lift his foot high like that. That certainly gives the ref discretion to send you off, especially when something happens at that speed. It's not a joke red like others in CL's past (van Persie's for Arsenal against Barca a couple years ago, in particular was terrible)