one of my best friends is an intj and he is easily one of the funniest people i know. it certainly has to do with timing and the ability to keep a straight face. i've watched him say the most offensive things and i've often had to explain to others that "he didn't mean it." he even gets an infp friend of ours laughing at his jokes, which is really impressive.
I love calling my brother up and telling him my new favorite most offensive joke. Such as:
What do you get when you stab a baby 100 times with a fork?
There's always this long pause during which I'm laughing at my own joke before he starts laughing.
My new one:
What sexual position do 9/10 people enjoy?
The difference between me and my INTP BF is that I know to only tell jokes like that to people that I know will laugh. But I have to work to curb my deadpan insults, along the lines of, "And that's why we all hate you." Or, "Yeah, how stupid were you?" People sometimes take it the wrong way and don't laugh.