Not the least because being offended is a blank check for anyone to define their own red line and impose them on others. And some people seem hyper sensitive...
Now you might not have realised it's offensive. You might disagree - you think it's fun, and legitimately believe most people think it's fun too. But once you've been told to stop, it's pretty clear. It's perfectly okay to be corrected and to learn. And it's normal to behave different with different people.
So it hardly seems like there's a big issue here.
And in this world of twitter lynching, feminist and political correctness mititantism, this is a blank check that you can bet will be cashed in.