A joke or not you have to be careful because someone might take offense when it deals with something they've been shunned for their whole life. I've failed classes because of religious purposes. A teacher of mine made my life hell in British Lit because she was Christian, and made me write a paper on the bible and then when I didn't write it on the positive side of the bible she failed me but yet I still ended up with a high enough grade in her class to make top 5% because I worked twice as hard as everyone else. Just be careful not to try to offend people on accident or not.