It was the threat of the bartender reaching for the bat. If the nazi didn't think there was a chance he'd actually use it, the threat wouldn't work.
The threat of violence is a deterrent to keep nazis from getting too bold, thinking they can do what they want without repercussion.
Some people think the threat of violent response is overreaction to someone who's just expressing their ideas. As a bisexual man, I think it's a pretty even response when those ideas are "hey, what if we rounded up you and everyone like you and marched you off to death camps?"
At the very least, you can never let them believe that you'll just roll over and let them do it.
Look, I respect your right to be how you are, but keep it in your church. I don't need to see it everywhere I go, and I damn sure don't want it anywhere near me. I don't have a problem with you, but if you try any of that God shit on me, I'm gonna put you on your ass, bro.