Punished for role playing?

Party got captured by a mob boss and his bandit dudes. We’re all tied up on our knees, mob boss says we’re being taken to some cells, maybe get ransomed or interrogated. My character spits at him when he finished his monologue, DM tells me that he orders his men to kill me while I’m prone and tied up. I’m restrained and prone, they roll a few attacks with swords, hit me unconscious, then a few more times while I’m down, killing my character. DM says the mob boss doesn’t like being disrespected. We were all level 3 and it was the first major fight that resulted in us getting captured. Guess I’ll make a new character? DM says it’s too bad because she liked my character, and asks if she wants to let the party find a cleric to revive me? Well then why did you kill her?

Edit: This was my first time trying DnD and this was our first session. The point of this post was to gauge whether this was normal and a thing to expect moving forward because it surprised me.