That's not causation, though. Parents who let their kids watch a lot of TV may also be less likely to act against bad behavior (by disciplining them, providing better models for behavior, and so forth). A large amount of TV-watching time could simply be an indicator of poor parenting, rather than the actual cause of bad behavior. I don't know whether or not this is the case, but I'm wary of studies that only look at surface-level correlations.

Edit: However, after a bit of searching I found this page which summarizes several results that go beyond basic correlation.

one of my biggest concerns is that the way things are presented is artificial, designed to manipulate the viewer into thinking the way the creators of the show or commercial want him or her to think

This is true, but I'm pretty sanguine about it. The reality is, my kids are going to live in a world where they are exposed to media manipulation - protecting them from it at a young age isn't going to encourage the kind of skepticism required to combat it later. Already, my almost-4-year-old seems to discount how awesome things look in a commercial due to past disappointments.