Filed at 6:11 p.m. ET WASHINGTON (AP) -- Republicans yanked a radio ad Thursday that was aimed at black voters in Kansas and Missouri comparing Social Security benefits to slavery reparations -- except paid to whites by blacks. It was the latest skirmish in a multistate war over Social Security ads pegged to November's congressional elections. The commercial was paid for by a Republican interest group and aired in the Kansas City area on an urban contemporary station whose listeners are predominantly black. GOPAC, which is headed by Oklahoma Gov. Frank Keating, said the ad was a mistake and withdrew...