For most of my life I knew of no joke that could offend me. Ethnic jokes, dead baby jokes, blonde jokes, "too soon" jokes-- I even found most of them funny.
Until a few days ago when I heard this one. I laughed, but only because it was so over the top and way past the line. In a way, it made me feel better about myself-- that I DO in fact have a line that shouldn't be crossed, and that it exists in reality, not just in theory.
I have it in the spoiler because it's so foul. Don't click unless you want to read it, and don't complain.