The best legal defense in a copyright suit may be to say that the infringement doesn't matter. That, at least, is the route that the Google Inc. (NASDAQ: GOOG) is taking in defending a suit from Viacom Inc. (NYSE: VIA).

"Viacom's complaint threatens the way hundreds of millions of people legitimately exchange information, news, entertainment, and political and artistic expression," The Wall Street Journal [subscription required] quotes Google as saying in a court document.

Fine. But what happened to addressing the issue of illegal posting of copyrighted video?

Google's response is that it takes down video when asked to. It is a bit like saying that a parking garage will call the police after people's cars are stolen. Let thieves steal the cars. We will try to recover them after they are gone.

The YouTube model was based, in part, on users posting content from media companies. Google knew that when it bought the video-sharing company. Now, the search giant is saying that it cannot be responsible for its users breaking the rules, even when it gives them the tools and distribution network to facilitate the actions.

Seems a little thin.

Douglas A. McIntyre is a partner at 24/7 Wall St.