Asians process certain foods differently from other groups of people. Just because they have metabolic factors that allow them to cope with MSGs, doesn’t mean other races of people do as well.
There is nothing unhealthy about salt or sugar. Unhealthiness comes from quantity, and it’s likely the quantity of MSG that is added to food that causes problems (just like too much salt, or too much sugar does). Also, MSG is just ONE form of Glutamic Acid, and thus its concentrated use in food is not natural. Food naturally contains Glutamic Acid in various forms, but never as one concentrated form.