Why? He spoke the truth, and that is not against any law here.
he simply stated truth as well, that if you do not like this country, you are free to leave.
murderoud Muslims just can't handle the truths in his letter, and they have no case.
The law and the truth have no relevance in the PC world, only what offends the selected and preferred thinkers as they self identify themselves.
Sure, he may be right and yes he could eventually win any case brought against him, but it will be a battle, his name will be sullied and it could cost him an arm and a leg.
But yes, you are right, no law was broken.