The money and time he is spending being entertained by them, is time and money that he is not spending on buying weapons and killing people.
They just do their job. And they are not hurting anyone with it.
Why get angry at them for singing a song?
Better get angry at countries that sold weapons to him.
That is actually being used to kill innocent people!
Apparantly it's difficult for people to be angry at America and other countries than it is to be angry at some artists making their living in an innocent way.