So this lady went to a restroom and I think I am going to steal her purse from her.
Wow, you were serious about stealing! What happened?
I have ethics, I was joking! I don't steal from people!
Joke or not, that was highly distasteful and could have caused a lot of distress to the people around you since you are now seen as a potential thief and might steal from them. You need to be more tactful or keep these jokes in private.
What is your problem. Why do you think that I am really some type of thief?
Well you stated in the beginning that you were going to steal a purse from a woman. I really hope you are just joking, but even if you are that is not really something to joke about. Hopefully you understand where I am coming from!