By Jarrett Renshaw and Steve Holland COLUMBIA, South Carolina (Reuters) -President Joe Biden on Saturday drew a stark contrast with top Republican rival Donald Trump, making the case that Trump failed to support the rights of Black citizens and represents a threat to the U.S economy and democracy. Biden’s comments came during a dinner on Saturday to celebrate elevating South Carolina and its large base of Black voters to first place in the Democratic Party’s calendar of contests to nominate a candidate for the November election. Biden rattled off a list of his accomplishments as president that…