Because atheists (of which I am one, just to be clear) are just as capable of seeing the value of human life despite their lack of belief in the supernatural, which I thought I made clear in my comment @JeffBurton. In short, mysticism is not a prerequisite for morality.Christians are called to be more Christ-like. Atheists are called to be more ... nothing. There is no analog in atheism for the goal of living your life as Christ taught. Atheism is a nullity. That's neither good nor bad, it just is.
The claim that atheists are just as likely as Christians to value any morality at all can be generalized into this claim: Goals are irrelevant in achieving things. Let's use something other than religion and apply the same logic.
My daughter plays club soccer. She can say to herself "I am a soccer player and I wish to be just like Kaka, the great Brazilian midfielder." Or she can say to herself, "I am a kid and to me, soccer is just one of many competing activities." The choice she makes will have major ramifications in her life. If she chooses one, she will work on ball control and power shots. She will end up as a starter on the team. If she chooses the other she will be just as likely to watch SpongeBob as anything else. She will end up riding the bench this year and be kicked off the team the next.
Let's rewrite that comment with this example.
Because kids (of which I am one, just to be clear) are just as capable of playing quality soccer despite their lack of devotion to the game, which I thought I made clear in my comment @JeffBurton. In short, dedication is not a prerequisite for skill.This is clearly nonsense.
Atheists most certainly have a strong argument when it comes to repeatable scientific experimentation. They have no argument at all when it comes to morality and it's an act of wishful thinking (faith?) to suggest that they do.