I just watched this video on YouTube 5 Unexplained Mysteries Of World War II! and was surprised that many viewers were almost enraged by the fact that the author said many times "the world war II" instead of just "world war II". Not being a native speaker of English, I was quite surprised and also ashamed because I say "the world war II" quite often. Now I understand that it's wrong to do so.
However, I still don't understand the reason. In the comments under that video, there was an argument brought up that "World war II" is a name - just like "Facebook" or "Tony" - and names are not to be used with "the". But I noticed that in Wikipedia, while the article on that war is titled as "World War II", another name for that war in the article is used with "the" quite often - "the second world war".
Also, I remember how Ed Sullivan was announcing the Beatles on his show: "Ladies and gentlemen, the Beatles" - he did use "the" then even though "Beatles" is a name.
So, why not "The World War II"? And why so many viewers were so angry? Does "The World war II" sound somewhat insulting to native English speakers?