Some people say watching tv is bad for children in all ways. Give your opinion.

Because it is popular, watching TV for entertainment has become a habit for people and affects their  daily lives. While the influence of watching TV on people is undisputed, an issue of debate is whether watching TV is beneficial for children to access to knowledge (you could also say "whether watching TV has educational benefits for children") . I am of the opinion that children can get knowledge from watching a variety of TV programs.
There is no doubt that most TV programs, like talk shows, historical documentaries, entertainment shows, sports news, political news and so forth are educational and meaningful, which is essential for children to gain knowledge and broaden their horizon as well. Take historical documentaries for example. Young students can learn historical knowledge from traditional classes, but it is difficult for them to master or understand some abstract historical culture and art just through the teaching in traditional classes. Now watching historical documentaries might be the best way to help them with understanding those arbitrary areas. It is one of the main reasons why multimedia has been introduced into our traditional classes.
Watching TV has long been regarded as a form of relaxation. When children feel frustrated or unhappy because of failing exams, or if they are under high pressure from tons of homework, watching TV can not only help them get rid of pressure and frustration so that they can continue to study efficiently, but can also improve more or less (Is this used to describe how much knowledge or the relationship to the fields in our daily lives? It may fit better after "is" in this sentence if you mean the second) knowledge which is related to all fields in our daily lives.
Despite those benefits, it should be noted that children might become ("become" is used instead of "be" since this is a conditional situation that may or may not happen in the future) addicted to watching TV. Besides, TV screens could be bad for their eyesight, especially when children sit in front of TV for hours in succession. However, those problems caused by watching TV can be solved by the management of parents.
From what has been discussed, one can conclude that watching TV is not only good for children to get knowledge, but also provides them with a way to relax (a reflexive pronoun like "themselves" is not needed with the verb "relax" here). What is more, the bad effects of watching TV on children can be controlled by their parents.