Hell I had a lot worse in middle east.
However if you really want to mess with their heads...
There is a way to make them go ballistic.
That is by sending a reply in the form of a copy of a exorcism prayer or the Christian statement of faith.
This is because they are so backwards and superstitious that they will receive the prayer as a greater insult than any threat of violence.
You could go on by telling him that his wudu is weak and he is full of jinns, etc. Have fun with it.