It's because most of people who don't have a speech impediment do "stutter" when they're in emotional distress. They might have slight repetitions when they're neverous or frightened. So they associate their experiences with yours because that's a common/easy way people are able to understand one another. The fact is that most non-stutterers have never met nor will ever meet a stutterer in their life. Unless they have a family member or had somebody in their class. We only make up about 1% of the population. Or so the stats say... So there's not much awareness of it aside from what's in movies. Not sure you should sue them for it. It's up to you whether or not you want that potential media attention or have the money for legal fees.