There's no doubt that M is the villain of the film. I don't even really consider Silva the villain, as he has far too little screen time to be the main villain and he's far less menacing (aside from the deformity) than M is for the duration of the film.
I mean I can understand your point, but I disagree with you. I mean yeah she gave Silva up but at the same time he was hacking and doing things and I am sure M told him to stop doing that and eventually she was like well, if he doesn't stop then I will just give him up so technically Silva was doing illegal things which weren't what the MI6 were supposed to do. Yes giving him up was definitely a little harsh, but Silva is definitely the villain in this movie no question. He is giving up the names of other agents and that has nothing to do with M. If he wanted to kill M he should have just went after her not other agents.
If that was all that M had done, I might be inclined to agree, but you're only touching one of the several despicable things that M does over the course of Skyfall. She sells out her own agents and the agents of England's allies by losing a disk that she should have never created in the first place. It's her actions by and large that cause the deaths of these agents. Had she been responsible and cared about doing her job in the correct way, their names wouldn't have been out in the open. She betrays Bond both in the PTS as well as by sending him out on assignment when he's not physically able to carry out the assignment (although that whole character "arc" is extremely half-baked and pointless), and she has the nerve to thumb her nose at the British government when they call her on her ineptitude and stupidity. Without M's arrogance and complete disregard for anyone in MI6 besides herself, Silva wouldn't have needed to even be in the picture. He's more of a tragic character than a villainous one, and one that M herself ultimately is responsible for creating.
