Sarah was trying to knock him down a few pegs, paint him as a guy with serious malfunction and cover up her 2-faced manipulation with the stock "but you know I love you and we're such good friends" card. She assumed he would play along in order to maintain civility in front of a crowd and lights like so many comedians and celebs would. She would put "their friendship" on the line and he would predictably meet her halfway in order to get those class-act points as expected.
She and her producer had previously calculated that it would get a lot of attention for her and her shitty unknown show. The brutal honesty, revealing quotes, the shockingly candid exposé! This was a hit-piece giftwrapped with an olive branch. Failproof.
Only he didn't fall for that or play along, he knew exactly what was going on. It was an ambush and he calmly called her out on it. He didn't feel bad for her show or her credibility dip because of what she was trying to do, he wasn't going to step in and graciously "save the show" in front of the audience by taking a velvet-lined character assassination bullet.
This is a tactic that's as old as a roach's balls, and several times less pleasant. This would have worked on basically everyone during the 90's when she probably pulled this asshole maneuver against every single one of her ex boyfriends. You could tell she had decades of practice, she had no idea it could even backfire. She didn't know him very well but knew that most people will act like they're your best buddy in front of other people if you declare it in front of them.
I'm glad he stood his ground and refused to sacrifice his self-respect as the "gesture of kindness" towards her trap she expected him to dive into.
The funny thing is nobody will trust her now. Good riddance