Seems legit. Show him the Leonardo Di Caprio documentary about "Titanic".

The fact they spelled it "Basterds" should be a clue that fact-checking was not a priority. Just take your boyfriend to the edge of the flat earth and push him off into the arms of Bigfoot and the Kraken.

Does he think that Abraham Lincoln was actually a vampire hunter as well?

Wait till he finds out that a couple of space cowboys saved earth from Armageddon by blowing up an asteroid.

You're dumping him because he has a belief that happens to not be true? I think there are bigger problems in your relationship

So? Why is it so wrong to believe in something? I agree with Commandokid - there's something else wrong with your relationship. I hope you do break up with him because he deserves better, deserves someone who will support him and his beliefs, instead of knocking them down, thinking they're stupid or ridiculous, and making him feel silly for having different beliefs than you, which based on how you tired to tell him differently and are so ready to end the relationship, I'm guessing that's how you treated him.

If you ever need to breakup with him, just say you're a lizard person who's research into him is over.

Show him a history book, tell him to educate himself

Y'all, it is a mostly true story. While it ended much differently, there was a group of Jewish men in the US army who really pulled many stunts similar to what was shown in the movie. While you should read books, The American Heroes Channel has great documentaries about wars in the past with actual footage and interviews with participants. Having seen Inglorious Basterds earlier, I had no idea it was partially based on a true story until I saw a show on AHC. After that, more research was necessary on my part.

One wrong belief is apparently a deal breaker. While I do agree it's ridiculous, I'm sure everyone believes at least one thing that isn't true and will defend it vehemently.