For centuries straight cisgender able-bodied white males determined what everyone would be called like a little girl on Christmas morning naming her dolls. Now as marginalized people begin asserting themselves it easy to offend someone. Even if you’re a good and kind person who would never do so intentionally. The wrong way to respond is to say it isn’t offensive. A little worse, would be to say people are too sensitive. And it is hard not to look like an ass saying "We're friends, we can joke around that way" or "It’s okay that I said it because one of my best friends is (insert race/sexual preference, ethnicity, etc). As a person of color I feel like I can provide insight into how many of us would prefer you responded. Copy this down and try it:
“I didn’t know that was offensive. I’m sorry. I won’t say it again.”
If you think you might be a victim of a social justice warrior politically correct witch hunt you can follow up with this question, “Why is it offensive?” We’re happy to explain it. There is always a reason. And usually we’ve put up with it for at least a century before we got up our nerve up to say something. I promise contrary to what FOX news and the right-wing blogosphere tells you, we’re not just making shit up to make you feel bad.
Getting defensive and arguing with the offended party about how they shouldn’t be offended is a request to have your privilege and superiority affirmed by that person. You’re telling a gay person that you know more about being gay, a black person that you understand the 400 years of the subjugation of their ancestors better than they do, and you’re asking a transgender person for permission to tell them who they are and how the world will see them. If you actually are as a good a person as you think you are, you won’t want to do that.
But if you still feel like you are being bullied by the word police you can just say “Okay” and roll your eyes after we look away. You’re not the first person to say whatever it is to us, at this point we can live without your enlightenment. We’ll settle for you just shutting up.