Not sure why you found that patronising. There’s a big difference in the arsenic content of rice milk (high) and rice crispies (not high).
If you had said you didn’t give your child rice milk, I wouldn’t have commented on it (though in a ten year old it’s probably still fine, they are much bigger relative to the amount of milk they drink). But you said rice crispies, and there is no evidence to back avoiding rice crispies.
It’s up to you what you give your own child, but if you are advising other parents not to give their children any rice products “because they’ll get arsenic poisoning”, don’t be surprised when other posters correct that advice.
The comment about polenta was aimed at the classist “why not baby led wean instead, on a nice piece of avocado” comments that pop up on EVERY baby rice thread. Including that wildly biased analytical armadillo link above, which is either completely scientifically illiterate, or deliberately scaremongering.
Baby rice is treated like it is literally poisonous on here, and while it’s a bit boring it is not going to do your baby any more harm as a weaning adjunct than stewed apple or pear will.