Is it legal or illegal to physically defend yourself from a verbal threat of bodily harm?

Had an argument with my brother and some others about self defense. I live in Michigan and he lives in Florida if context is requested. We were playing DnD which resulted in a group argument about a situation.

If someone approaches you and says something along the lines of "Give me your money or your teeth." are you allowed to defend yourself or are you required by law to walk away.

Everyone in the group, besides my brother, stated they would defend themselves as this is a verbal threat of physical harm, attempted robbery and coercion. Their attempt with their defense would be to knock out the assailant.

My brother was adamant that it didn't matter if it was technically legal or illegal and would most defiantly result a conviction against you for battery.

My brother also argued that technically demanding/asking for someone's teeth isn't a threat of physical violence, as the person never technically stated they would take the teeth or physically assault them.

So his argument is to try to walk away/leave the situation and not physically retaliate until there is some kind of proof of crime against the aggressor. I find this argument to be highly idiotic because this is the point of no return. IF the aggressor gives you physical proof of a crime in this scenario it's likely to be the carried out "give me your teeth" portion, of which either you receive great bodily harm or death from. Them attempting to hit you, you blocking/dodging then swinging back provides the same amount of physical evidence as you striking them after their demand for your teeth. The only proof you can really have in this scenario is your own physical injury.

Sadly every attempt at searching for self defense laws and cases results in stand your ground and castle doctrine laws. So all I have been getting is something along the lines of "can I shoot someone for x", and nothing about attempting to knock out someone for making a verbal threat of bodily/great bodily harm.