It is my considered opinion that, while TV has a potential for neutrality and an equal potential for good (in fact, often exercises both those potentials), it has a presently active influence for harm (and an even greater potential for negative influence that is often fulfilled).
Two specific examples, the first example relates to what I call billycrystalism and the second to something Tolstoy lamented, the shaping of women's roles and attire to align with those of "women of the street." Billy Crystal made a fabulous career out of snide witticism and--coming from him--such are amusing to some and down right funny to others. What is neither funny nor amusing is hearing parents, for example, toss billycrystalisms at their 3-year-olds then congratulate each other for being so profoundly amusing while the child cringes in humiliation, confusion and shame. This is an absolutely true and direct negative influence of TV as Billy Crystal's old movies are shown on TV.
The other is how visual images impact the development of mental constructs of self--this negative influence is confirmed by the controversy in the modeling industry and by national governments implementing corrective measures around the world--that manifest in how girls and women dress, groom, walk, stand, and in general deport themselves and, sadly, it all falls along the same lines as that which Tolstoy lamented (I believe the title in which he addresses this is Family Happiness, 1853.)
Therefore, while TV has a potential for neutrality and even good, its present state realizes its equal potential for harm and has been doing so at an accelerating rate for at least three decades.