Ah well, humor is a little difficult to judge, to be honest. Specially online, even when I don't know if that is the case. But I agree with you that sometimes the responses are exaggerated. People seem to be eager for an excuse to be offended. I don't get it.
I hope you can solve the problems with whomever lashed out at you. Of course, telling them that you understand it was a dumb joke will probably help.
IF it helps, I don't think you are a narcissist. *glomps DC*