Why did straight guy tell me I am gay?

I just met a guy introduced to me by my friend in a club in Los Angeles. He was very controlling around me and acted as if he was my bossy big brother. He was being very touchy towards me as well, and kept grabbing me so I would follow him.At the end of the evening he randomly told me that I was gay, and that he was straight. I told him I was not gay, but he kept saying like stop hiding it etc. The irony is that there was nothing to suggest to him that I am gay, as I am very conservative, and don't like to display any kind of public affection(the exact opposite of him!), and I don't act stereotypical gay. He then saying that I was hitting on him and that I grabbed his ass, I did not grab his ass in fact he grabbed mine(thought he did grab other guys asses and probably girls as well). He could not come up with any reason why he thought I was gay. One of the strangest thing I have ever witnessed.