Is everything else ok? How bad was the argument? Does it happen often? How old are you guys? Breaking up with someone you really like or love is a big decision and while making fun of your stutter is a major infraction, if you guys are young and everything else is good then I don’t think it’s breakup worthy but if it’s a habit or if he does a second time after you made it clear how it’s a line he can’t cross then you really have no choice but to