1.) It's not a big deal; they're trying to make it one to play the victim against big bad evil Trump.
2.) It doesn't matter who created it.
3.) They're liberals at CNN, so I am sure they feel perfectly justified crying victim to make themselves feel better because Trump is a bully, or something. Journalists fancy themselves martyrs and heroes because once in awhile one gets themselves killed in a war zone or be being stupid, and anyone who questions that delusion is the enemy and is just inciting violence.
4.) They're liberals. The ends justify the means. If that means outing some asshat (who most likely did not create the video Trump tweeted to begin with) to "defend" themselves, they will do it. CNN doesn't even understand how stupid they come off looking by threatening to out the person if he doesn't behave himself to their satisfaction ad infinitum.