I would say corn is grain, and it is used to fatten farm animals prior to slaughter and the yanks use it to make high fructose corn syrup, which is cheap, and probably one of the biggest dietary problems the yanks have.
And no I generally don't eat rice. May be once a month or even less, only on the occasion I might go out for Chinese or something. Probably only had rice once this year that I can think of.
Treat it like alcohol small amouts on the odd social occasion.