You can write any conditions you want into a license.

That's what actually differentiates proprietary licenses from open-source licenses.
Open-source licenses follow certain rules, and you usually select an existing license, so therefore they can be reasoned about, collectively. People often implicitly mean "OSI-approved license", when they talk of "open-source licenses".
Proprietary licenses, on the other hand, can contain whatever bullcrap you want.

Having said that, I'm not a lawyer, but I imagine, if you also called your license "GNU General Public License", then a case could probably be made in court, that your license is deliberately confusing.

You can write any term you want for your software. There have been instances of people adding terms to their licensing like "You hereby accept to forfeit your soul's ownership to the creator of this software."

Enforcing it is a different problem.

I just like to interject for a moment. What you're referring to as butthole is in fact GNU/butthole, or as I've recently taken to calling it, GNU+butthole.

Fun fact: Buttholes are unique in the same way that fingerprints are. So resubmitting with a new picture can be used as proof of identification and thereby licensing.

Why do I know this, you wonder? Eons ago I stumbled across this anus recognition software source base. The idea was that it could one day be used for identification instead of retina scanning.

In reality, no one worth extorting is going to use a non OSI approved license (or license and exception).

That said, the JSON license says JSON must not be used for evil. Is it any coincidence Google made protobuf as a JSON alternative??

The GPL states that its text must not be modified. I take this to mean (though I'm no lawboy), that if you wanted to have a license with the same terms plus some changes (the butthole rule), you would have to rewrite the whole thing. It would not nearly be a "GPL license".

This is very important nitpicking I'm doing here, okay?

NAL, but I think it won't be considered open-source, as it violates rule 5 of the open-source definition. What if the person does not want to share butt-hole? Doesn't the license discriminate that people sharing butt-hole pics are only permitted to use this software? What if they don't have a butt-hole to begin with, and use a colostomy bag? What if they shit and bleed in the same hole, cuz they were fused at birth? It is also not enforceable. What if the party in question shares their painted navel, their wrinkly skin, or their reproductive organ (foreskin tip, vaginal canal) as the butt-hole? They could also share the butthole of a dog or a horse? You will also have to issue stool samples and ass-tissue samples? I'd recommend that you consult a lawyer who specializes in shitty laws.

I've added a "Everyone except Bob Smith can use this software" a la "fuck Anish Kapoor" clauses for paint colors before.

Though honestly it would be hard to enforce.

Creative works are better served by Creative Commons licenses instead of software licenses.

You can use whatever license you want. You can even go ahead and write your own license from scratch.

You'd only have to worry about enforcing the license, especially when you include such unorthodox terms and conditions.