Wednesday night in Las WVegas, Mayor Mike Bloomberg learned what it is like to be thrown up against a wall and frisked. At the opening of the Democratic debate, his first, Mayor Mike was greeted by his nearest neighbor on stage, Sen. Elizabeth Warren, with this warm welcome: “We’re running against … a billionaire who calls women ‘fat broads’ and ‘horse-faced lesbians.’ And, no, I’m not talking…