I only saw it once a while ago, but I don't think they were portrayed as 'bad guys' in the film. They even came out in support of how their story was told in the movie.
To me it portrayed them as money-grabbing, egotistical and a bit moronic. Is it possible that the film manages to re-inforce whatever views the watcher had before seeing the film, I wonder what somebody who had never heard of those twins before seeing the film would think of them.
I knew the story of them and Zuckerberg before seeing the film, and I still came out with a negative impression of Z and a more positive one of the Ws (and definitely Eduardo). Yes, they weren't as bright as Z, but I felt like they tried to deal with him in good faith and he just screwed them, Eduardo and anyone else he needed to in order to get to the top.
I did feel like the movie was trying to make me empathise with Z over the others which I didn't really like; at the end when the lawyer tells him that he's not an asshole, I found it artificial because I couldn't see what on earth had led her to that conclusion.
YMMV though, it seems to be quite polarising and you may well be right that it's based on existing perceptions; I didn't sympathise with the Ws in real life, but then I wasn't a huge fan of Z either.
I"m sure they can come across as egotistical and arrogant. I'm sure they're super competitive. Hell, they placed 6 in the olympics in 2008[1], and will probably row in 2012. These are kids that, yeah, they have been given a lot, but they also know how to compete. And rich to begin with. Thus probably arrogant as hell.
Is that because in the end we are rooting for Zuckerberg?
I mean I could understand 'naive' and even understand dislike for kids who come from old money.
Yet money-grabbig/egotistical is a bit weird to parse. Heck if it was a kid from lesser beginnings and he fought back, he would have been the hero of the movie.
I'm not a huge fan of Zuckerberg in real life - I admire what he's done, but not his personality. But in the movie, he's written to be the hero, a hero with flaws certainly but hero none-the-less. So yes that's certainly part of it, but just as he was written to be the hero, so too were the twins written to be the bad guys, even if they weren't as bad as we might expect hollywood villains to be.
I don't think egos is weird to parse, they didn't just come from money (incidentally I come from money, to a lesser extent, so that doesn't set me automatically against people), they were the type of people that think their coming from money makes them superior in more ways that just their bank account balance.
As to money-grabbing, it's my opinion both from the actual story and also the movie, that they frankly didn't deserve the money they got from Facebook, so yeah they were money-grabbing in their legal pursuits.
When I saw the movie the movie I thought they were depicted as two useless, uncapable boys whose only advantage in life seems to be 'My dad has lots of money and connections'.
In fact in a scene, the Zuckerberg character says 'The winklevoss are suing me only because, first time in their life things are not going as they desire'. That almost means they are used to getting easy money and making others work for their luxury and that didn't happen this time and they met someone far more intelligent, capable and hardworking who doesn't need 'Dad's money and influence' to win in the world. And he can do that on merely merit, while they can't.