Do you consider me a banana? Do you even know what banana really means? Are you aware that it is a highly insulting and derogatory word?
For people who don't know me to make such insult is at least understandable, but you can't! You should know better! And if I'm really a banana I wouldn't care, but I'm not! Therefore you have insulted me and have grossly hurt my feelings.
I hereby demand your apology, and I think this is the least you could do.