If you want to get people to let their guard down, be agreeable. Draw them out. Smile and nod. Let them hang themselves with their own words. That's a journalistic skill.
If you just want to be angry at them, well, write a letter. Yell at them at the phone.
With that in mind, is he there to 1) Let his guests know how much he agrees or disagrees with them? 2) Get them to say whatever and find out who they really are?
It's fine if you like and listen to Rogan. Maybe he's grown since then. I think it's less fine to pretend like bad things didn't happen, aren't bad, or that Rogan is a journalist luring his friends to hang themselves by confessing misdeeds.
You should watch or read someone like Hunter S. Thompson interview people he despises. He got his yucks on with Nixon, and this is a guy who purportedly trained his dog to savage a cloth dummy at the word "Nixon." You smile and laugh and let people hang themselves.
Similarly, I've heard the most shameful and shocking things from people you wouldn't guess, because I am told I have a very non-judgemental demeanor. Father Confessor jokes have been made, and I faintly smile and raise my eyebrows, and then people tell me about drinking a full steaming stein of their own urine. I've heard worse, far worse. People like to unburden themselves.
And therefore, if someone doesn't judge -> scold right then and there, why, there's no judgment at all.
I submit that this is not true.