GENEVA (Reuters) - The U.N. High Commissioner for Human Rights launched a thinly veiled attack on U.S. Republican presidential front-runner Donald Trump and other presidential hopefuls on Friday, in a speech entitled “The road to violence.” “Bigotry is not proof of strong leadership. It is evidence of the lowest and most craven lack of faith in the principles that uphold a ‘land of the free’,” Zeid Ra’ad al Hussein said in a speech at a university in Cleveland, Ohio.  “Less than 150 miles away from where I speak, a front-running candidate to be President of this country declared, just a few months ago, his enthusiastic support for torture,... inflicting intolerable pain on people, in order to force them to deliver or invent information that they may not have.  “We have heard hateful slander of foreigners, and multiple candidates declaring their support for extensive and intrusive surveillance of people based on their religious beliefs – vast and discriminatory systems to single out and discriminate against Muslims.” Zeid’s speech, the Klatsky Lecture at Case Western Reserve University, also recalled the Nazi holocaust and the genocide of Bosnian Muslims for which former Bosnian Serb leader Radovan Karadzic was jailed last month.  He said the eyes of the world would be on Cleveland when it hosts the Republican National Convention in July, and it was his “deepest hope” that Americans would use it to demonstrate their profound understanding of human dignity and human rights. “And yet, in what may be a crucial election for leadership of this country later this year, we have seen a full-frontal attack – disguised as courageous taboo-busting – on some fundamental, hard-won tenets of decency and social cohesion that have come to be accepted by American society.” He said the price for the “dangerously divisive” rhetoric would be paid by innocent people falling victim to violent acts, not by politicians. “We have heard these calls to hatred – calls stigmatizing and demonizing minorities, beginning the validation of violence,” he said. “Real courage would mean standing up for the great and enduring values of this society.”   