Grains are Chametz, not Kitniyot
Maize is not Chametz and is only Kitniyot because someone made a mistake.
If you’re going to kvetch about terminology, at least get your terminology correct. You seem to trust Wikipedia, so go read the first sentence of the Wikipedia entry for maize and then come back and tell me it’s not a grain.
Also, grains are NOT chometz. Chometz is the result of wetting the flour of a certain subset of grains (wheat, spelt, barley, rye, and oats) and allowing that mixture to rise (e.g., by leaving it in that condition for longer than 18 minutes).
Maize is kitniyos because its flour can be confused for flour that can produce chometz. Your repeated argument that someone made a “mistake” therefore only strengthens the case that it is kitniyos.