we will always have adversaries who are not negotiable. This may be one of those. In the scope th te whole public spectrum, they are far, few and inbwtween. The best you can do is ignore them. That is what most mainstrean people do with extremists. I would let them say what they want.
Don't think for a nanao-second these type of people didn't critique gandhi or MLK or Jesus. They did, but no one listen and those that did were too small to mean much. I know it is disturbing, but let it sleep and that is where it will stay! Sleeping!