Making fun of my stutter was and is a redline; anyone who crosses it is out of my life. Period. No exceptions, no do-overs. If you want to salvage this relationship, then you need to communicate to him that his actions crossed a line and hurt you and it won’t be tolerated. Would he find it “cute and funny” if you made fun of the size of his “boyhood” (I use that term because if he’s making fun of your stutter, he’s no man)? I doubt he would. And it’s the same with your speech. If he cares for you and values you, he’ll listen, apologize, and never do it again. If he says you’re “overreacting to a joke,” then he’s told you everything you need to know about him. Dump him and move on; he ain’t the one. Don’t for a SINGLE MOMENT think you took it too seriously.