The likelihood that he didn't know he was going to do this, even if perhaps it was a surprise on the day, seems pretty low. He allowed him to do it. I really don't believe the guy showed up dressed ina Dr Phil costume, presumably hours before taping, and was able to sit around in the green room and go past all the producers and make it on set if this was going to be a real problem for them. Doubtless if they didn't contrive the entire thing themselves then they likely saw it as a gift.

If I recall Dr Phil refused to interview him, and made a big show of kicking him off the set. On the face of it this makes him look bad and seems to prove the guy's point. I guess he either thought he'd still appear high and mighty by refusing to indulge him, (yet suspiciously waiting until he's literally on stage to do it) despite the apparent statement it made. Or maybe they figured it would just make such good ratings that it really didn't matter if you allowed him to make a negative commentary about Dr Phil that probably goes over most of the audience's head because the visuals alone would draw people in and could be milked for the program trailers.