Why did Churchill believe the Munich Pact was the "beginning of the reckoning"?

The Munich Pact signed by Germany, Great Britain, and France allowing Hitler to annex a portion of Czechoslovakia despite the Soviet Union willing to aid Czech. in defense against Germany. This pact set an action of appeasement which worried Churchill as a beginning to an end. Churchill and Neville Chamberlain disagreed on the merits of Hitler ruling Germany. Churchill would have much preferred a communist state and interference over that of Nazism, which he viewed as dangerous. Chamberlain believed Hitler would be good and stabilizing for Germany. Ultimately, the pact did not work as Hitler would move to annex the entirety of Czech. and then invade Poland which will lead to the beginning of World War II on the European front.