I hate reading about studies only in mass media outlets because of the lack of critical evaluation. Unfortunately the real study isn't showing up in the Circulation journal's past three issues and they never did give the complete title.
However, even the LA Times article states "researchers found a statistical relationship between long hours of TV viewing and a shortened life span, but the study did not go so far as to find a direct cause".
This means the results are interesting and the subject should be further evaluated in a controlled study, but are useless for practical purposes. We don't know if it was the sedentary behavior or something else, like the potato chips and soda that often go with watching TV. It may be that their conclusion is correct, but it's impossible to know from this type of study.