We have a First Amendment which enshrines their right to say what they said. We have free speech, but speech is not consequence-free. I am aware of no amendment which prevents those of us watching from forming quite negative opinions about those who celebrate hate and murder.
Those opinions will make many of us Islamophobes, one supposes. How could it not? Don't you suppose that dislike will be reflected in less subtle discrimination? Comments about being in a hole and refraining from further digging apply in this case.