Yes, you had WW2, but there are arguments of history that the Holocaust could have ended early if Allied bombers targeted Concentration camps, rail lines leading to the camps, and disabled their holocaust system. In other words, the Allies fought the bad guy but they weren't saints. Countries had to fight the Nazis to avoid being conquered, invaded and losing their civilization to them! It's like I'm on a ship and if the sink sinks then I fall with the rest of the ship, so it's in my best interest to save the ship, whether or not I actually care about anyone else on board. Lots of wars and contests are based on this principle as well, Abraham Lincoln did not end slavery because he cared about Blacks and Churchill didn't fight the Nazis because he cared about the Jews. They do what they need to do and their interests are served in the process. That being said;
Winston Churchill made a famine that killed up to 3 Million Indians:
en.wikipedia.org
They are not taking down the statue because of he fought the Nazis. They are taking it down because of this, and possibly other issues.
However, I do not personally agree with them taking down Winston Churchill. I am a fan of this wartime PM, and have viewed Crown, The Darkest Hour (2017), Dunkirk (2017), and love historical drama recreations of him brought back to life. I love his speech from the Dunkirk time and appreciate how he took power and lead the country. However, I won't call him a saint. He's a reflection of a war-time era in the past, one that I never lived through. A statue taken down will not undo the movies, documentary, TV-shows that to me are a zillion more times powerful than a statue. That being said, I don't have strong feelings either way and feel the artistic renditions in audio-visual are more powerful than a statue.