I believe some MSG is still made with this and causes migraines and other heart issues, it's mostly phased out though, and can cause mixed reactions as the type of MSG isn't labelled, let alone MSG.
Until you can provide a shred of evidence for that I will assume you're just adding a layer of legitimate-sounding abstraction to the same superstition. Toxic precursors =/= toxic end products. This is chemistry, not alchemy.
Is MSG safe to eat?
FDA considers the addition of MSG to foods to be “generally recognized as safe” (GRAS).
https://www.fda.gov/food/ingredientspackaginglabeling/foodad...
I buy shakers of it, it can be delicious in some meals.
That said glutamate is a neurotransmitter, so yeah you probably shouldn't inject large quantities or anything.