The truth is common property. You can't distinguish your group by doing things that are rational, and believing things that are true.
It would seem that if no other humans are behaving rationality and your group is behaving rationally then even Sesame St could tell you which of these things is not the same.
If no other groups of humans are behaving as rationally as yours is, then it's likely no other humans are capable of easily identifying that your group is the one with the high level of uniquely rational behavior. To the extent that other groups can identify rational behaviors of yours, they will have already adopted them and will not consider you unique for having adopted them too.
You can signal the uniqueness your group by believing and doing things that are both rational and unpopular, but to most outsiders this only signals uniqueness, not rationality...
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