The point is not that you should be able to ban humor in one place or another.
The point is that you should be free to perform humor in another place and not have that bleed over in the place where it is banned and have repercussions there.
It's the same reason why so many authors since time immemorial wrote pseudonymously
Humor is not banned and nor should it be. But maybe, to avoid confusion we could make humourus posts have a * or someting? And maybe humor can live in a separate section of the site so it doesn't mix with the other content. But if it still doesn't work I think we all know of a final solution for humor.
Maybe we could have a different upvote system, like marking a post +1 Funny vs +1 Insightful. Then users could adjust their own personal scoring if they don't want to see humorous posts.