I don't approve of slavery, kidnapping, rape or infanticide.
Can God use something that we call bad to accomplish his purposes? He used the assyrians to punish Israel and then he punished the assyrians.
Do atheists have morals? Of course! Even though they don't believe in God they can still do good.
These things feel similar. A good God can use evil; a person who doesn't believe can do good.
But how do I live my life knowing this? Even though I don't fully understand God's ways or the atheists unbelief, I will love both and use my life to serve others and have interesting conversations. But the change and growth comes from God so I try not to be attached to the results, as hard as that is!