Who says he knows it's from War Games? Lots of catch phrases become idiomatic in popular culture without people knowing the origin of the phrase. How many times do you quote Shakespeare inadvertently?
If I quote Shakespeare, it's because it is familiar to me because I read the play that the quote was from. How do you quote a line like this without knowing or seeing the movie? I didn't think that line was so popular outside the movie context but I could be wrong.