What complicates the war against MSG in getting it regulated by the FDA is that it is so confusing how glutamates formed, and how they can be safe to eat or harmful. I don't think the word "MSG" really should be used to refer what we're up against. While explaining to my husband that, sure, there's nothing wrong with pectin, in and of itself, yet even when no MSG is added to a product with pectin in it, pectin still produces "mirror image" glutamates and carcinogens in processing, as do all the other ingredients which are not harmful in and of themselves; but once they're an ingredient in a product and the product is processed, it produces free glutamtes. So, perhaps "free glutamates" is a better word for the antagonist than MSG, because even when MSG is not added, glutamates, the harmful substance in MSG (not the sodium) are spontaneously produced during processing, from innocent ingredients.
Another confusion is, yes, glutamates are essential for our functioning. However, we don't need to ingest them, as our body naturally produces glutamates. Additionally, glutamates are found naturally in protein or meats. But if we eat a natural turkey, the process by which glutamates enter our system is eons slower than the free glutamates in processed food (which processed glutamates subsequently flood our brain and excite our brain cells to the point of death.)
So, he wanted a chemical molecule of what exactly it is we're talking about, so here it is. But, yes, trying to explain what it is that we're trying to avoid is confusing!