Mixing and Meanness
There's a hidden similarity that causes confusion between the Christian admonition to accept those who are different and the worldly admonition for the Church to accept the World as equals and to intermix soulishly and spiritually with their ideas. If we did mix, the World can't in any good way take on the things of the Church, so the Church would always take on the things of the World in order to mix our ideas together on equal footing.
There is a similar confusion: Differences between people - even personal moral rules that don't violate or speak to revealed truth - should not keep Christians apart. Violations of revealed truth, however, should. Both these rules are revealed truth (1 Corinthians). Unity is better than uniformity.
Jesus put up with people different from Himself - us; Christians. He did not put up with the World. Christ ate with people who wanted to know God and who knew they were sinners; He did not become party friends with those who were settled against God! We do not mix with the World just because Jesus ate with sinners - understanding the meaning of what occurred then now pulls the rug out from under anti-Christ worldlings who cause compromise from the pulpit!