On its face, there isn’t inherently anything wrong with having overtly partisan tv stations. In practice, though, it leads to ever-increasing hyper partisanship, increasing polarization, and a willingness to pander instead of being factual.
Fox News is a really good example. It was, obviously, always an explicitly right-wing channel and more than willing to dabble in pushing little bits of misinformation here and there, but did have some reporters who were willing to hold ‘their’ side to account too.
Then along came Trump, and every reporter who was unwilling to uncritically promote dangerous lies were either forced out or resigned, despite being right wing voters themselves. Even Trump’s biggest defenders on the channel knew he was a liar and a fraud (see, for example, Tucker Carlson’s leaked text
messages) but they recognized (again, explicitly stated in leaked text messages) that their audiences didn’t want the truth, they wanted to have their biases confirmed.
For that reason, I’ll always prefer news sources that at least strive for balance and will watch them instead of sources that aim to promote opinions I agree with.