The person who doesn't realize you were joking and is OFFENDED!
Some people just can't help it. Everything on the internet pisses them off. In this person's mind, everyone is 100% sincere all the time, and it is this person's job; nay, it is their CRUSADE, to defend the dignity of anyone who might theoretically be offended by something someone somewhere said sometime (whoa! try translating that sentence into French, will ya?!).
They'll leap to arms in the defense of children, who shouldn't even be on Facebook to be offended by the joke in the first place:
They'll leap to the defense of other races, especially in instances where absolutely nothing offensive has been said:
And don't even think about mentioning the word "gay" in any context without a visit from the Mysterious and Ineffective Gay Rights Crusader:
Wait ... what?
The "Offended!" is easy to identify because she is often showing up to defend someone other than herself. She's never personally offended; rather, she's offended on behalf of some other group that she thinks OUGHT to be offended by your joke. The joke that she completely missed. Because she's way too busy crusading against injustice to be bothered with things like getting jokes and not making everyone around her miserable.
But this person, however eye-rollingly irritating, has nothing on the last one on our list ...
The person who understands perfectly that you were joking, but CHOOSES TO GET OFFENDED ANYWAY
This person is the worst of the worst. The cherry on top of the poo-poo sundae. The one that makes you shake your head so hard you get a migraine.
I'm talking about the people who morally reproach you just like the person in the above examples, but they open with the hated words "Look, I know you're just joking, but ..."
It is impossible to follow that phrase with anything that doesn't sound like you're scolding a grade-schooler. It cannot be done.
"Look, I know you're just joking, but even by 'joking' that women are worse than men at math, you are perpetuating a stereotype that many women (and men) are working tirelessly to overcome. To even joke about something like that is to lend legitimacy to the stereotype, allowing society to continue to cling to it."
Also, this comeback is at least as effective, if not MORE effective, when used against a man. Just something to keep in your pocket.
Scolding adults is an activity with a 100% failure rate. Have you ever seen someone respond with something like "hey, you're right, that joke was really insensitive. Thanks for taking the time to point that out to me. I'll make sure to sanitize all my jokes in the future so that no one dead or alive could possibly be offended by them" -- but in a non-sarcastic way? Because I haven't. The response is always ugly.
I would much rather have 100 people who don't get the joke shrieking at me about how cats actually make GREAT pets or how Canada is a WONDERFUL place to live and I shouldn't insult it (duh, I WAS BORN THERE) than listen to one single asshole opine about how they know I'm joking but really think that I ought to reconsider my material, because, you know, Canadians take a lot of flak and you have to be the change you want to see in the world, wouldn't you agree?
ZING AGAIN!!!! I am on FIRE today!
I'll always just bring it back to their sandy vagina. Always.
There are, of course, much more effective ways to let someone know they might want to reel it in a little -- like, for starters, don't laugh at the joke. Maybe boo it. Don't encourage it. Walk out. Roll your eyes and shake your head. Being up-in-arms all the time is bad for your blood pressure.
Also, look at this picture of a panda having a party in utero. Because it's not offensive to anyone, and sometimes inoffensive is the way to go:
This elephant fetus is all partied out, though.
Quick, someone draw a penis on his face! He's passed out. Rules are rules.
Haha! Okay, I'm done.