Objective morality

Atheists and Christians often argue about what makes morality 'objective', and whether you need God for morality to be 'objective'. But what does 'objective' in 'objective morality' mean, exactly? And why is a world without God unable to express whatever it means?

Instead of answering this directly, I'd prefer to imagine a situation that makes morality pack the most 'punch' out of any situation I can imagine.

This is the situation: suppose that humans are made to be perfectly loving towards each other and relate to one another in an 'ideal' way. So it's impossible to really live out your nature without relating to others in an 'ideal' way. That way, even though doing evil can make people happy, no one can really be themselves - who they really are - without relating to others in an 'ideal' way.

This situation would seem to make morality pack quite a punch. So maybe morality is more' objective' if this situation is the case than if it's not. Also, clearly, it's easier to believe this if you're a religious person plus you believe that things have somehow 'gone off the rails' for humanity so that, somehow, no one lives out their true nature in a complete way (at least in this life).