@Tukker - what is causing the governor to set a citizen to an entertainer is the fact that you are growing on the same turn as you get a cultural expansion. On a cultural expansion with growth, the governor automatically reassigns old citizens as well as assigning the new citizen, and he won't set them in such a way that the town will riot next turn.
There are no settings that will help you. The only way to prevent him from setting a clown is to make sure the town will be happy even after growth - turn up the luxury slider the turn before growth, for example.
Note that this is the only time it is necessary to turn up the slider before growth - if you are not getting a cultural expansion at the same time as growth, then you should not adjust the slider until after growth.
There are no settings that will help you. The only way to prevent him from setting a clown is to make sure the town will be happy even after growth - turn up the luxury slider the turn before growth, for example.
Note that this is the only time it is necessary to turn up the slider before growth - if you are not getting a cultural expansion at the same time as growth, then you should not adjust the slider until after growth.