I hesitate to add this because it's anecdotal, but I have had more than one person tell me of restaurants that say no MSG on the front window, but when passing behind the restaurant, noting empty cartons of MSG.

The prejudice comes in when people then assume all Chinese restaurants are therefore dishonest, discounting that restaurants everywhere are capable of being a bit dishonest ... Kangaroo meat in burgers, selling pork as veal... Frozen food sold as fresh. Just watch a Gordon Ramsey show.