I don't find it hilarious at all. It's like watching a cheap joke, where the joke is more on the one who makes it. Imagine some Real Madrid reject mocking Messi, or Iniesta, or Xavi like that. It's funny only because Ronaldo is from Real Madrid. If the situation had been reversed, than it would've been anything but funny.
That's entirely different. I'm not a public figure, so I have more liberties than a professional footballer. If I like to drink 10 cans of beer for example I can do it without any kind of restrictions. If you're a footballer, or a public figure, you have certain limitations on what you can, and can't do. Some break those limits, like Mourinho, Cristiano Ronaldo, Ibrahimovic. However, what Deulofeu did is even worse. It's bad for Wenger and Mourinho to mock each others and act like dicks, but at least they do it from similar positions in terms of status. Not the case with Deulofeu. Some are arrogant, but also have the results to back-up the arrogance. Some are arrogant, without having any kind of result to at least make that arrogance somewhat acceptable. So, bottom line, Mourinho, Cristiano, Ibrahimovic, are arogant types. But they also have charisma, impressive results, and winner mentalities. Deloufeu is just arrogant and childish.
First you have to do stuff to be arrogant AND successful.