Like many other protests of Israel's campaign in Gaza, this one ended badly — police had to cool an ugly fight between supporters of Israel and Gaza, breaking up the warring sides as their screaming and chanting threatened to turn into something worse. But some protesters at this rally in Fort Lauderdale, Fla., took their rhetoric a step further, calling for the extermination of Israel — and of Jews. Separated by battle lines and a stream of rush-hour traffic outside a federal courthouse last week, at least 200 pro-Palestinian demonstrators faced off against a smaller crowd of Israel supporters.