Say it like how it is.
Black girls are black girls!
Have SEX on the registration form, we don't need to change to GENDER.
I also think no joke is inappropriate given the right context. However, as a human race (one who has developed advance language as a tool) we need to education our young on becoming aware of our own interpretation of the meaning of words. Mainly, we are responsible for making up the meaning of the word we hear/read, not the person who is saying the words. And it should human-being's number one priority to listen to what others are saying.
Just listen.
People who take offense to any verbal/written communication are just NOT emotionally matured, and they may want to take offense, and that is ok. It is certainly their rights and choice to do so.
Verbal abuse doesn't exist, it is just a figment of imagination.