I don't give much of a fuck how they changed the story. I don't think that movies have a responsibility to be exactly like the story. It just means that the book is not the movie, and actually should remain that way even if they don't change anything because a book experience is very different from a movie experience. Like I robot is not at all the same story as in the book. I don't like I robot the movie, but I am not pointing a finger at the movie and screaming, "You are not I robot! You lie! Liar!"
But I like that V is neither the villian nor the hero in the movie, and that he isn't just interested in anarchy. I can't think of any anarchist I respect. The movie's message as far as I can see is that life is not so simple that it can be divided into good and evil. And it invites the watcher to scrutenize their ethics, and the ethics of their leaders.