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.
I cooked vegan at home for a long time (I'm not actually an ethical vegan, I just like vegan food). Konbu dashi will give you similar glutamate profiles, but tomatoes, fermented products like shoyu and miso, etc are simple ways to boost the umami as well. Usually the biggest trick in good vegan food is to understand how to balance all of the flavours. Meat based cooking has so many savoury flavours, and if you simply cut out the meat, you end up with overly sweet/sour dishes. They lack depth. If you're designing a dish and you are waiting until the end to figure out how to get the umami in (for example, by adding MSG), then you're really not going to succeed most of the time IMHO. If I want a savoury dish, umami is where I start.
Having said that, I've never made a vegan burger style dish that I've thought was particularly good. I've had some excellent vegan dishes like that at restaurants and I've always wondered how they did it. Since MSG triggers migraines in me, I'm pretty sure it wasn't MSG :-)
[0]http://www.fda.gov/food/ingredientspackaginglabeling/foodadd...
http://science.jrank.org/pages/4433/Monosodium-Glutamate-MSG...
Producing a URL with the word "science" in it ending in .org is not sufficient evidence. Find a single empirical datapoint or published study, otherwise stop spreading fearmongering speculation. Do you concern yourself with which table salt to buy because it may be "bad NaCl"?