Considering that Conan pulled out a respirator for Alec, it looks like a set-up.
Here's what happened according to the RW site Media Research
On the December 11 NBC show host Conan O’Brien wrapped up his interview with Baldwin by asking Baldwin about Clinton’s plight. Baldwin answers but as he proceeds his voice rises as he jumps up from his chair and is screaming and flailing his arms by the time he’s finished. Cutting to the punch line, O’Brien then jumps up and puts an air mask over Baldwin’s mouth to calm him down. Funny political satire or, even if meant in jest, mean-spirited and violence-inciting words that would be condemned if uttered by a conservative?
Here’s the exchange as transcribed by MRC news analyst Paul Smith.
Conan O’Brien: "Before we leave, I gotta ask you. It’s no secret that you are very political. You are a very political person. It’s no secret that you have actually had some associations with the Clintons. That you’re a liberal man and I thought you know today, this is a historic day and you’re one of the most politically active actors out there. What do you think?"
Alec Baldwin: "I was in Africa. I go to Africa. I mean ladies and gentlemen I am in Africa. For three months I am in the bush and I come back. I come back here and I come back to what? I mean what is happening right now as we speak? Right now the Judiciary Committee, the President has an approval rating of 68 percent. The President is very popular and things are going pretty good and they are voting to impeach the President. They voted on one article of impeachment already. And I come back from Africa to stained dresses and cigars and this and impeachment. I am thinking to myself in other countries they are laughing at us twenty four hours a day and I’m thinking to myself if we were in other countries, we would all right now, all of us together,
all of us together would go down to Washington and we would stone Henry Hyde to death! We would stone him to death! Wait! Shut up! Shut up! No shut up! I’m not finished. We would stone Henry Hyde to death and we would go to their homes and we’d kill their wives and their children. We would kill their families. What is happening in this country? What is happening? UGHHH UGHHH!!!!"
http://www.mediaresearch.org/cyberalerts/1998/cyb19981215.asp