After another day of closed-door testimony in Washington, Former FBI Director James Comey weighed in on President Trump's recent tweet calling Michael Cohen "a rat." "It undermines the rule of law," Comey said. "This is the president of the U.S. calling a witness who is cooperating with his own Justice Department a 'rat.' Say that again to yourself at home and remind yourself where we have ended up. This is not about Republicans and Democrats. This is about -- what does it mean to be an American?