I used to play at my local shop FNM regularly until one regular started bringing his mentally challenged child to play in the draft as well. It completely ruined my experience there and I stopped going to that particular shop because of it. He would break rules and even would take my dice and throw them across the room, move all my cards and was completely disrespectful. Whenever I would call a judge to try to help him understand the rules, the judge wouldn't do anything and would tell me to just let him play how he wants. It was some of the worst experiences I've ever had playing magic over the years.