If absolutely necessary, I would have used it to defend myself. I would have tried to not use it if at all possible. I had it with me because I was practicing with it in my spare room at the time that I heard the commotion. Given that the guy was probably twice my weight and a foot taller than me, I thought it prudent to take it with me, just in case.
The goal would have been to restore harmony in that situation, without resorting to violence. As it happens, this is what occured, I didn't have to get directly involved, and I learned something valuable in the process. It all worked out well.