"Peoples" is definitely not a word
And to satisfy my curiosity I doubled checked in OED....and peoples is most definitely not a word
So yes, anyone using it is gramatically incorrect.
The one that really gets my goat is "he should of done it"
there is no verb 'to of' the verb is indeed "to have"...."he should
have done it"
anything else is just so ignorant it's actually painful, lol