Christians are not called to be isolationist isolating themselves from the world.
They are also not called to be separatist separating themselves from only certain people like family or friends or even the church.
They are called to be socialist, that is they are called to be social and blend into the crowd not to be like the crowd but that the crowd might be like them. That they might see their light and if not be encouraged to change at least to see truth and know what it is.
If a Christian is an isolationist or a separatist, then they are simply not mature enough yet to know their true identity in Christ.
Be the light, like a city on a hill and shine his reflected glory for all were meant to see it not just a few or none at all.