I think you may have missed their message. That they self censored for fear of violent retaliation makes strong ridicule of the threatening group. It exemplifies its contrast with a free society.

It essentially says, "They are so lacking of basic compassion that even jokes are not allowed."

That's the joke.

It also highlights to normal society that there are indeed people whose beliefs are so absurd that they get worked up and want to kill people over a stick figure.