Parent poster a-french-anon may be wrong or at least is making unsubstantiated wishful claims about costs and benefits - "the errors would be extremely rare" - would they really? And would they be evenly spread over in-groups and out-groups?

But at least the question "how is that acceptable?" is in fact a question of a moral nature. It's unacceptable, but it is unacceptable because it is immoral.