I feel like it should be isst, saying he frisst, even though he is eating a butterfly, still seems rude.
True, but "er" might be "der Hund"; and dogs "fressen", so that would be fine.
If Duolingo wants er to mean an animal, there needs to be an indication of such. Otherwise, the term could just as likely refer to a human, therefore it would be isst and not frisst. Both should be accepted without a cause for distinction
Er means human. But human frisst???? Frisst isn't matching word or?
So...is it never correct to use 'isst' here?