Their words are being broadcast. If they say unkind things about someone they should expect to be judged by viewers. If they say unkind things about someone regarding a trait that person can't help, they should expect to be judged harshly. Ian's friends and family are hearing what they say and when Ian gets out of the house he will too. It's hurtful, thoughtless, and immature behavior.
I understand that tics, whether they be stimming, vocalizing, stuttering, etc., can make people uncomfortable. But you're on a damn TV show. Either keep your thoughts to yourself or face the consequences. T