what are we supposed to say again when christians ask us where we get our morality?

[Rampant.A.I.]

I would reply good people existed before Christianity. Mr. Hitchens also made a great point on this subject when he asked if murder, theft, and adultery were acceptable before the Decalogue. There are moral and ethical people in this community that do not believe.

That’s not even the point; the point is that you have no way of determining if a person is doing good deeds or evil deeds if no God exists.

That's your claim. You need to logically support this claim, otherwise it can and will continue to be dismissed out of hand.

Are you capable of presenting an argument to support this?

Hint: "Nuuuuh but you dunno whar yur moral come frum an um a geddum frum mah bible" is not good enough.

You've already been told:

Social principles beneficial to a tribal animal.
Evolved empathy.

Both are displayed in other nonhuman species. You claim these must come from God in humans, but have yet to tell us why you believe this, and support it with a compelling argument backed by evidence.