If you mean 'proper manner' I think it has to do with 'propriety'. From the Longman dictionary: correctness of 'social or moral behaviour'.
I presume, societies with mixed cultural traits are much harder to obtain a norm of 'proper manner'. Therefore, to me, it seems that according to behavioral traits, 'birds of a feather shall flock together', not otherwise.
Proper behaviour is different in Dubai, different in Thessaloniki, different in Novosibirsk. It's pointless to attempt defining a global 'proper manner'. Societies run far more efficient when 'birds of a feather' do flock together. I guess my point is clear enough.
That's my view regarding the 'proper social manner'