There are many slang words for your private parts. Too bad the guy chose one you don't like. Just let him know you prefer "pussy". That's all you have to do.
What is more worrying is that he didn't necessarily think it was yours. Are you exclusive with him and you think he has more women sending pics like these?
Now, I am going to say something quite old-fashioned and I expect I'll be flamed as being out of touch, but here goes anyway. I am feeling brave today.
Whilst my past history would not depict me as a delicate Victorian maiden
and I know times have changed a lot since I was young, I just think that a guy being able to ask for something like this and get maybe dozens of women complying just encourages him to become jaded and spoiled and for you to seem like just another easy-to-manipulate woman.
You are too good for this. I think that's why you are upset. Take some time out and meditate on this. Explore why you are so upset. I think you may find that deep down in your soul, you feel like you are being treated like a piece of meat for this guy's entertainment, no matter how cool this is supposed to be nowadays.
Your reaction to the ugly word he used about your body speaks volumes. You want to be more special than that. You deserve to be more special. Treat yourself the way you want people to treat you and you'll find they often do.
One day when you are happily married to the guy of your dreams, you will be glad that there aren't guys out there posting pictures of your private parts all over the internet for any perv to get his rocks off to. As will your husband, I'm sure.
(ducks down...awaits flaming...)