For those who don't know, here's some background to the video...
Burt Reynolds had recently divorced his wife, Loni Anderson.
Here they are together:
Jay Leno had been making fun of Burt's divorce during his Tonight Show monologue. I think at one point Burt didn't want to appear on the tonight show because of Leno's jokes. Well eventually Burt came around and made an appearance, but not before Leno made another joke about Burt. However, when Burt came on he was cool and acted normal.
Then Marc Summers comes on. Now Burt is already pissed off, so every little thing was ticking him off even when he felt that Marc had his back turned to him. Usually the guest sits facing front to the audience, but Marc had his back turned to Burt. Maybe it was intentional, maybe it wasn't. Burt called Marc out and Marc came back with a joke about Burt's marriage. That really, really, really ticked of Burt.