I'm currently reading a book called "Facebook The Inside Story" and while it's definitely an anti-Facebook perspective it illustrates a number of ways the movie was unfair to Mark.
The biggest problem, to me, was suggesting that Mark basically stole the concept from the Winklevoss twins. The book traces the origins of the idea and clarifies the context. Things like: there are many other similar social networks, a boy at Mark's previous school had created and shared a "Facebook" project, the Harvard school newspaper was explicitly calling for the creation of a school wide Facebook (and that call inspired Mark to try and create one first), etc. It's less like he stole the idea from the Winklevoss twins and more like the idea was out there in many ways. What he did to the Winklevoss twins was tell them he was working on their project while working on his own intentionally trying to derail them.
> The biggest problem, to me, was suggesting that Mark basically stole the concept from the Winklevoss twins.
I don't think the film suggests that at all. It says the Winklevoss think this, of course. But it doesn't agree with them.
> What he did to the Winklevoss twins was tell them he was working on their project while working on his own intentionally trying to derail them.
That's also exactly what the movie says. The film is on the Winklevoss's side at all - it makes them look ridiculous for thinking their "innovative" idea is that a harvard.edu address is exclusive. They're douchebags who want to make a website to put on the internet what is already happening at the Finals clubs (buses bringing in hot women to party with harvard legacies).
The part of the film that I thought was the biggest problem was that it framed the whole Facebook project as Mark's way to deal with loneliness. The film starts with him being dumped by Erica. The film ends with him refreshing (pathetically) the pending friend request to her on Facebook.
In reality he had a long term girlfriend when he started developing Facebook and she is now his wife.
Mark maybe a socially awkward human who doesn't quite understand that Facebook has become a weird perversion of actual social interaction, but he is not alone the way the film constantly repeats (Eduardo: "I was your only friend")
I agree with you that the film also slights Zuckerberg by suggesting he has few or no friends and was creating Facebook over a girl. There are a number of things I think the film "gets wrong". The removal of Saverin made a lot more sense to me in reading the Facebook book I referenced above compared to when I saw the movie - where it felt much more like betraying a friend.
When I saw the film I did get the impression that it supported the "Mark stole the idea from Winklevoss twins" narrative. Granted, I saw it years ago and I may be remembering things incorrectly, but that's what I (remember that I) took away from it.
A big concept that I think the movie "gets wrong" (scare quotes because the movie successfully tells an entertaining story and isn't trying to be a faithful history, so the movie isn't exactly wrong, just not reflective of reality) is the focus on the drama with the twins, Saverin, and Mark. The book spends much more time with Facebook design decisions and a broader cast.
The movie's narrower focus on a few main characters and their drama makes it seem like the consequential moments of Facebook's history are things like getting the idea from the Winklevoss twins. The movie thinks more about a spark of an idea - Facebook, whereas the book thinks more about taking a prototype and turning it into a big business. I think the latter is more of what is important about Facebook.
The biggest problem, to me, was suggesting that Mark basically stole the concept from the Winklevoss twins. The book traces the origins of the idea and clarifies the context. Things like: there are many other similar social networks, a boy at Mark's previous school had created and shared a "Facebook" project, the Harvard school newspaper was explicitly calling for the creation of a school wide Facebook (and that call inspired Mark to try and create one first), etc. It's less like he stole the idea from the Winklevoss twins and more like the idea was out there in many ways. What he did to the Winklevoss twins was tell them he was working on their project while working on his own intentionally trying to derail them.