Between saas bahu and nand bhabi relationships even constructive criticism is not beneficial, you wouldn’t want your BIL or FIL doing that to you, or would you? But may be it’s different for men, may be they don’t care much.
If one is so keen on teaching then they should do this by their own actions and not by embarrassing them. You can even beat your own kids[desi style] but with someone else’s kid you can’t do the same,(not that you should beat your kids) but that reminds me of this auntie in Pakistan who used to beat her 30 years old son with shoes.