Think a good example of exhibition etiquette is watching any of Floyd's now numerous exhibition matches. He goes in fully with the idea of having fun, clowning his opponent (who are always overmatched), and having this "agree to fuck around at medium" fight. However, as is often the case, whoever he's fighting tends to get in their head that they can go at this old man hard, and when they do, he drops the clown around smacks them around hard.
You can watch almost any of his exhibition fights and if there comes a point where the guy he's fighting looks like they might actually hurt him, he fucks them up and tries to get them out of there.
It's right around the 9 minute mark where Floyd almost gets chinned by a hard punch, and you can see the switch flip to "time to get this idiot out of there", and then he does.