"It's open season when someone stutters" - does your family stutter too? I don't get it. I don't know if I'd cause a scene, but I'd inform them that stuttering is the result of a dopamine imbalance much like tourettes and I'd ask them if they'd be making fun of someone with tourettes. I mean if it's not okay to be making fun of someone who twitches then why make fun of someone who stutters?