No inanimate object can influence a person; it is what the person does with this inanimate object that can cause problems. The passive watching of television has been scientifically studied and a person's brain waves are less active than if that person reads, for instance. So, sitting before a television set for hours and hours is not as stimulating to one's brain as activities in which there is engagement. And, as others have already stated, there are educational and informative programs which provide learning opportunities for people. The greatest danger of the medium of television is probably on the news channels which present slanted reports whether on the liberal or conservative sides; also they do not always provide full coverage of issues and, thus, mislead the public. So, at times the television becomes a propaganda machine, especially if the viewer depends upon it for all his/her information. In addition, there are programs that are suggestive of immoral conduct which certainly are inappropriate for young viewers who may be affected by them.
As in all things, this depends on the extent. As Aristotle said, everything is good in moderation but bad when done excessively. TV programs (even trashy ones) can lead to family talks about serious moral issues or problems that face young people today. So it's an overstatement to say that it's all bad.
While television can be less intellectually stimulating than other activities, I wouldn't go so far as to say it stops people from thinking. That is a very extreme statement. You might be able to find evidence to support the idea that too much TV is damaging, but I doubt you will be able to support the statement that TV stops people from thinking.
I realize that some families tune into the television and tune out from each other, but that isn't always the case. As a child, my family would gather around the TV and watch certain programs together. Then, we would talk about the show around the dinner table. Sometimes television can be a great educational tool. Sometimes it can bring families closer together. Again, your statement seems a bit extreme. I can't agree with such a blanket statement that TV ruins all families.
Ever since I was a child, I've been lucky enough to be able to use TV as a background (like music) to my other activities--homework, reading, grading papers, etc. If this doesn't work for you, turn it off until you complete your necessary work. It certainly can be addictive, but TV is controllable. I believe parents should probably limit daily viewing time for their children, who need to spend important time on studies and outdoor exercise. As another post mentioned, TV can be educational and informative--it just depends on what channel you choose to watch.
Nothing stops people from thinking; that's a personal choice. TV does influence thought, but I think it does so in both good and bad ways. On the negative side, TV causes people to be more consumer oriented, and to want things that they don't really need, which makes them dissatisfied with what they already have.
On the other hand, TV can help educate and inform people and broaden their worldview. I don't think TV is inherently good or bad, it's how you use it.