Disclaimer: I am not referencing Batman: The Dark Knight in this post.
One thing I have noted with many unkind jokes, is that they are based on something mean that the joker thinks.
What if I thought Seth's hair was awful when he dyed it? (My bro, for a play, 2012)
I could have said "Seth, your hair is horrendous. Just kidding." The "joke" would have been based on truth.
Bob is pitching to Tom who is batting, and Tom thinks, "he is not very good at pitching." It could be easy for Tom to say, "you should take pitching lessons from me... Kidding!" Or Tom might sarcastically say "You're good at pitching."
The previous insults are based on truth, which not only hurts the receiver more, but also tells what the joker is thinking. In the case of sarcasm though, usually the statement is opposite of the thought. When I see it, I wonder how often I do the same.
If our lives were fully centered around following in Christ's footsteps, then how different would our jokes be?