Churchill claimed he never criticized a policy later that he had not publicly criticized when it was first raised. True, he was often on both sides of issues, and could pick his criticisms accordingly. But he in time he usually arrived at the right conclusions.
Regardless of whether you like the movie—and Jeremy Irons gives it an authentic, watchable flavor—we know much more about Munich in the light of scholarship since. We know that Soviet Russia was prepared to stand with Czechoslovakia in 1938, and had become a German ally in 1939. We know how—with the help of Czech armaments—Poland was eradicated in three weeks, the Low Countries in eighteen days, France in six weeks. If resisting Hitler was so ludicrous an idea in 1938, what was there about fighting him in 1939-40 that made it preferable? Given what we know, we are obliged to consider Churchill’s opinion—which was, characteristically, far from baseless.
"The power of the Executive to cast a man into prison without formulating any charge known to the law, and particularly to deny him judgement by his peers for an indefinite period, is in the highest degree odious….Nothing can be more abhorrent to democracy than to imprison a person or keep him in prison because he is unpopular. This is really the test of civilisation." —WSC