I agree with the almost all your points except about them stealing ideas. Ripping off the same game from indie developers is wrong. It isn't them using basic ideas like a top nav or usernames, there are examples of them copying entire games[1].
1. http://www.forbes.com/sites/insertcoin/2012/01/25/everything...
My argument is that Zynga stole another band's style and lyrics but changed the presentation slightly. They did not build on the 'basic ideas' like having a certain set of instruments.
By "basic ideas" I assume you mean "ideas that are better and more useful, and therefore more widely ripped off."
Your argument reminds me of when people say such-and-such band is so original -- yet it's another four guys playing guitar, bass, drums and vocals.