Racism in any form is unacceptable. And to so casually remark that you'll tone it down doesn't come close to sounding sincere. In my opinion you don't get a second chance when it comes to blatant racist remarks. It's NOT funny! And like Maya Angelou says, "When someone shows you who they are, believe them the first time."
We don't need anyone in here who jokes about stuff like that. If you're joking about it...you believe it. My 2 cents.