They don't make movies to please the actors. The actors are doing jobs and in most cases get payed a hell of a lot of money for doing so. As much as i like I like Ian McKellen, he should have got over himself, finished the job without complaint and then collected his enormous paycheck

Under regular circumstances I would agree with you, but he was in all the other Lord of the Rings films too where it was basically a family working together to make a movie, The Hobbit was completely different in its formation and I'm sure he was very let down by it based on his previous experience.. obviously he still sucked it up though since the movies finished, but it is perfectly fine for him to not be happy about it

You can have actors working together and green screens too, just on the set for the hobbit they didn't so they could make the height easier instead of using strange camera angles