[moogleii]

Sure, and you could say the same about tomatoes. But, generally speaking, people don't have reactions to tomatoes. The oddity/absurdity is spending extraneous resources/time arguing whether being allergic to MSG is actually a thing, just as it would be to devote resources into whether being allergic to tomatoes is a thing (hell, it's borderline as absurd as studying if being allergic to salt is a thing, at which point you would just be dead).

If you're allergic to tomatoes or salt, then it's a personal thing, not a general property of tomatoes or salt.