Cyanide is also a naturally occurring chemical found in food items like Cassava and to a lesser extent, potatoes. That didn't make it harmless.
We've pretty clear evidence of harm from certain doses of cyanide. We don't have it for MSG, despite a whole lot of trying.
Some people have a lower tolerance than "most people", for any given chemical, MSG included.
I don't think this sentence has any meaning. What is "the same order of magnitude"? By the normal definition (still not great, but at least it's well-defined), 6 times x is only in the same order of magnitude as x when x is in the range [0,1.7), and it's in the next order of magnitude up when x is in [1.7,10). Even if we adjust that to a log scale, 6x is in the same order of magnitude when x is in the interval [0,0.23] and in the next higher order of magnitude when x is in (0.23, 1).
This is not a solid foundation for the idea that "six times is in the same order of magnitude", even if we think the sentence is interpretable.
Still, the point stands - a 6x difference between normally-served dose and a harmful one is way too small to call it non-harmful. How do you even define a normally-served dose? This needs further clarification with better definitions.
We happily accept a 1.5-2x margin for Tylenol.
If you accidentally put 6x the normal amount of MSG in some fried rice, you’re gonna know about it.
The underlying message that some restaurants might plausibly put 6x the MSG of the standard dose comes across just fine and it doesn’t need to be nitpicked to hell.
Heuristics are a mental shortcut, not evidence themselves.
Where did you hear that potatoes contained cyanide?
Sadly, almonds that taste of something have become much harder to find.