Do you realize the irony in this statement? This is the exact problem with mass surveillance. Neither Snowden nor the NSA should be able to ignore the law, grab everything they have access to, and justify it by saying the good outweighs the bad. That isn't how the law is supposed to work. These restrictions apply to both good and bad guys.
The people who are defending Snowden's actions with this logic are using the exact same line of thinking that inspired these programs in the first place.