Republican front-runner Donald Trump called into CNN Tuesday morning to discuss his proposal to block all Muslims from entering the United States, and the interview quickly turned into an all-out war of words as the real estate mogul fended off criticism of his controversial plan.

“Your proposition is plain,” said CNN’s Chris Cuomo, “ban all Muslims until we can figure out what’s going on. People are asking you how you would do that? I say let’s put that to the side. It’s irrelevant. It’s about the concept.”