You're starting from the base that we live in God's universe so that atheists in that world are just in denial.
Yes. That is because we are trying to reason and think rationally, and the only possible foundation of reason and intelligibility is that Jesus is Lord.
values are ever changing out of necessity
So what you're saying is that:
--child rape was once good
--preferring lies to truth was once good
--adhering to theism was once good
--throwing atheists in big pits covered with deadly snakes was once good
Correct?
And how did you come to this conclusion about values ever changing? How do you know?
otherwise a group of people cannot live in harmony
But it isn't a moral duty to live in harmony with others, correct?
The real question is whether it's possible for these values to have developed naturally or not.
I'd say a more real question is whether other people even exist and whether your senses are reliable.