Actually, what you're establishing here is that you cannot make an objective observation at all...
Okay, by which mean is Federer cocky or arrogant? Because he's trying to pull off trick shots in his matches? We could argue for a long time, but statistically, he has lost very few rallies when he tried one; by quid facti (matter of facts), he's showing us his shot selection was sufficient to overcome his opponent. Djokovic, Dabhul (don't know the spelling), Wawrinka... everyone he tried it against has not lasted longer in the tournament to tell anyone Federer was wrong to do that. As far as strategy is concerned, you're always playing within a margin and, even if your shot is risky, if you keep pulling it off, there's no reason to stop it.
Is it because he acknowledges his ability to perform better than any other human being? Because, actually, he DOES hit a tennis ball better in more various ways than any other did before him, so we can't speak of him as being arrogant for telling the truth, nor for doing what he is good at doing. The problem with you is that you have yet to understand what means "humility"; it's not pretending to be lesser than yourself as this is a lack of confidence or, if conscious, a lie; it's not pretending you are better than you are as this is arrogance. Being humble is pretending to be who you are; not better, not lesser: exactly you.
I do not have any problem with a hockey player going for a shot, even in a 3 on 1 situation; however, he'll have to make sure his action is justified and it can only be the right move if this movement provided his team with the highest probabilities of scoring - if he hits the post, gets a dangerous rebound or scores, his movement may happen to look selfish at first glance, may be just for the show, but if it worked well, no one can say anything about it.
Federer is a bit like that; yes, he goes for highlights shots, but he can do them and, yes, if you were wondering, he keeps training for the specific purpose of being able to hit the ball in every possible way. As you have quickly noticed yesterday, even if misses some by times (those are mostly fancy drop shots, sliced passing shots or things like that), it puts him in the rhythm of going for more. And, if you were to play a tennis match and begun to feel a bit more lazy, trying something complex, something hard, when you are in a good position to do it... this may actually get you on your run. Everyone is pride when they pull those things off and it has a psychological impact over your game, even if you just get close to doing it.
I don't know why people say he's arrogant: what he does works; what he says in interviews are honest analysis; and he behaves with the most strict politeness I have yet seen on a court. What I can understand however is that those people who keep insulting him can hardly get a word out of any ethical theory, let alone understanding epistemology...