I'm going to send a rude message to my friend
Why would you send a rude message to your friend?
He's too nosy about my personal life.
You should be nice to your friend. Speak to him in person about it and don't be rude.
If he's going to be rude to me then I'm going to be rude to him.
Being rude to each other doesn't solve anything. You should talk to him in a calm manner. That way he can understand how you feel.