It is hard to become a "Great person" in a democratic country, were the ballot box and a free press, media these days, exist. Winston Churchill made history and wrote about it. His writings are huge, detailed, and very informative. Some of the best documented insight into the way it was. It was his personal will and stance that guided the British and its allies, the Canadians, the Australians, the New Zealanders, the Indians, the Maltese and so on, to maintain a hostile attitude against Hitler and the Nazis. It was his drive and never say die attitude that enabled the fightback that would eventually culminate in victory against the Axis forces. Without the British and its allies blockade and its strategic importance in the fight to win the war in Europe in particular. It is impossible to imagine a scenario, based on the realities of the day, other than what happened, that would have prevented a Nazis dominated Europe and probably the World in a decade or two.
I believe his comment was in his usually witty response to his bigger than life demeanour and not any deep seated dark villainous attitude that some others would wish it to be.