You are mistaken. Antony spent too much time lollygagging with Cleopatra, which was all the rope Caesar needed to hang him. And the Greeks were hospitable to just about anyone thanks to their abiding pre-Christian
belief that Zeus walked among men, and would punish anyone who mistreated him.
As to fellowship between groups... was there no trade between Mediterranean countries? I agree that families of different religions would be unlikely to marry into one another, but that is an issue distinct from different races coming together -- which would have been rather easy given the enormous variety of races brought under the political, economic, and often religious banner of as during their imperial age.
Not for nothing, but have you ever read any pre-Christian history? Or do you always assume that everything good finds it's source in the Bible? Even with a lack of proof to support yourself?