The problem isn't that simple. Most mainstream news, including CNN, have traded in objective reporting for idealogical dissemination. You can very often, legitimately call CNN "not credible". Just in the last couple years they have:

1. Told their viewers that it was illegal to read the DNC emails leaked to Wikileaks themselves, and to just listen to what CNN has to say about them.

2. Got caught posing one of their cameramen as a protester/rioter for an interview about why he was "in the streets".

3. Deceptively edited a video of Trump dumping fish food into a koi pond to omit the fact that he was following the Japanese PM's lead, then spent a whole day talking about how disrespectful it was.

4. Spent a whole morning talking about how Trump drinks diet coke, while there was an active terrorist attack in NY.

That's just what I pulled off the top of my head, too.

Edit: to the user that downvoted my comment: which of the four bullet points was false? It's easy to protect the liars who benefit our goals. It takes intellectual honesty to criticize one's allies.