I've been an activist for nine years. Whether online or in the streets, I've been campaigning, advocating and debating things like peacemaking, poverty reduction, environmental protection and religious freedom.
My motives are Christian: I believe this is what Jesus wants me to do. Still, I've stood side by side with atheists, agnostics, Muslims, New Agers, Buddhists and others in a common fight for a better world for all.
I've found that activism for peace and justice can serve the role of a common denominator and a platform for cooperation between different worldviews and beliefs. That's why it plays such a prevalent role in different ecumenical and interreligious councils. We might not agree on who God is, but we all agree that no child should starve to death.
It's the reason many non-Christians will agree with Christians on one thing concerning Jesus: that he was a good moral teacher. Morality can be viewed as one of the least exclusive claim of any religion. In fact, it can be viewed as one of the least religious! I've had several friends who, when they doubt their Christian faith, becomes activists for a while and emphasises Jesus' ethical teaching, before leaving the faith altogether and becoming atheists or agnostics.
So for a long time, I have viewed certain activist dogmas such as human rights and human dignity as self-evident truths that nobody seriously can question. I thought that everybody, except a few bewildered neo-Nazis perhaps, viewed them as objectively true.
But then I encountered some who didn't. They were all atheists.
In apologetics, there's an argument for God's existence called the moral argument. It basically says that if atheism is true, moral values can't be objectively true. They can't be facts. Instead, they are merely the result of sociobiological evolution. In other words, they're dependent on human minds rather than being true no matter what people think.
If there indeed are objective moral facts, such as rape and racism being evil while peace and compassion being good, atheism has a problem. Why do these facts exist independently of human opinion?
If "genocide is wrong" is an objective fact even if a genocidal dictatorship would gain world domination and convince everyone that genocide was right, what's the atheist explanation for that?
Atheists typically reply to this in two different ways. Either they'll say that objective moral facts simply exist without any explanation, they're just "out there" in a platonic realm.
But why do they exist? How did homo sapiens discover these facts? Why do we have duty to follow them? And what are the odds that the moral facts that exist are adapted after human beings rather than alien beings with entirely different living habits? If we're not designed, why do moral facts seem to be designed for us?
Alternatively, atheists will simply deny that objective moral facts exist. These atheists will often say that there's no evidence for objective moral values, and that morality is purely subjective. Whatever an individual thinks is good is actually good, there is no external point of reference. Laws and the court system are just social constructs that have practical value, but they don't correspond to any actual Law of good and evil.