Hate speech is still protected speech. You either agree all citizens need protection or you don't. Sure the guy may have been an idiot for not taking better care of his anonymity and posting on a public forum. It's one thing to be outed by fellow posters, and it's quite another to have a corporation do it out of pettiness and then announcing to the world. But it's post citizen's United and corporations are people too, so I guess the behavior is consistent with that decision.
But anonymity isn't protected. No one is preventing the slug from posting again. CNN won't try to stop him. They'll just report on him. He can do what he does, and they can do what they do.
I don't repeatedly post my "deepest darkest secrets" with like-minded trolls on the Internet, thereby propagating them. And, frankly, I don't really have deep, dark secrets; at least none that anyone would find interesting or threatening.
When has CNN ever walked into an occupy wallstreet or ANTIFA rally and theatened to out people for anti semetic signs? They are threatening to ruin some random guy on the internets life, all because they want to link it to Trump, you see that behaviour as Appropriate from a so called news outlet? How many death threats do you think this guy would have gotten if CNN decided to Dox him?
I don't know. But this was antisemitism directed against its own employees. I would expect a responsible employer to take care of its own. Seriously, who's the snowflake now? All they did was return the volley. Gently. I'd have gone for points.
The real problem with taking on trolls in the basement of Reddit for CNN is that the Reddit community does not put up with mainstream media threatening them... and the typical response is to Dox the employees of the media network... handing out confidential information on the employees such as their cell phone number, home addresses, unknown social media handles, etc. The response of CNN is not an example of "a responsible employer to take care of its own" -- it actually places the employees at CNN in a very exposed position.