A question on ELL recently aroused a discussion.
It's about usage of nationality as mass noun:
Like the Chinese, the Italian is a born gambler.
"You want to know why the Italian is skinny?"
The asker says, in a comment:
I was once told that we can think of other species collectively as thus we can use either The hippopotamus (singular) or The hippopotamuses (plural), but we can't do that with people.
I have never heard of this rule. Sure stereotyping is a slippery slope but not forbidden as such. What's with this rule? Am I missing something? Is this usage grammatically correct but politically incorrect or something like that?