I worked at the Apple Store for 3 years and every now and then I would stutter. Most people never said anything and those that did were mostly clueless as to it being a stutter and just a random slip on words. Only a few were straight up rude and to those I would say “If you can’t speak with someone who’s has a stutter with some courtesy you can’t wait for the next appointment in X hours” (depending how much of a jerk they were). They would apologize profusely very quickly.