It surprised me that Watchmen kept almost precisely the same sexual content of the comic. There's an attempted rape, and several instances of regular sexual congress, including a failed start. It's funny that they'd keep Dr. Manhattan's full frontal nudity, and all the sex, not to mention the increased violence, blood and gore, but they completely excised smoking by any sympathetic character. Only the comedian and the crime lord in the prison smoke, and they're both villains. In the comic, Silk's Spectre's smoking leads to some significant dialogue and a decent joke.
Our moral watchmen have deemed extremely gruesome murder is more acceptable than smoking. I'm not in favour of smoking by a long shot, but smoking on your own is far more ethical than rape, murder, and torture.