By Jonathan S. Tobin American conservatives have gotten to the point where they are often unmoved by efforts by their liberal antagonists to get them to disavow extremists on the far-right. The existence of hateful and dangerously extreme groups, including those that spread antisemitism, is a problem that needs to be confronted, however small their numbers may be. So deep is the distrust between the two sides in the tribal culture war that passes for political discourse these days that they assume every such request is merely a setup. They see no reason to comment on people who are wholly...