Can Atheists be ethical?
The answer to this question is a definite, "Yes." Atheists are people who, whether they like it or not, have the law of God written on their hearts (Rom. 2:15). They are subject to the same laws of our country (and other countries) and they have a sense of right and wrong. They often work with people who are religious and have ethical standards as well as non-believers who are don't. So they are exposed to all sorts of moral behavior. In addition, they often form their own moral standards based on what suits them. Besides, robbery, lying, stealing, etc., can get you imprisoned, so it is practical and logical for an atheist to be ethical and work within the norms of social behavior. How ever you want to look at it, atheists, generally, are honest, hardworking people.
Nevertheless, some Christians raise the question, "What is to prevent an atheist from murdering and stealing? After all, they have no fear of God and no absolute moral code." The answer is simple: Atheists are capable of governing their own moral behavior and getting along in society the same as anyone else.
At the risk of labeling the atheist as self-centered, it does not serve the best interests of an atheist to murder and steal since it would not take long before he was imprisoned and/or killed for his actions. Basically, society will only put up with so much if it is to function smoothly. So, if an atheist wants to get along and have a nice life, murdering and stealing won't accomplish it. It makes sense for him to be honest, work hard, pay his bills, and get along with others. Basically, he has to adopt a set of ethics common to society in order to do that. Belief in God is not a requirement for ethical behavior or an enjoyable life.
On the other hand
Atheists' morals are not absolute. They do not have a set of moral laws from an absolute God by which right and wrong are judged. But, they do live in societies that have legal systems with a codified set of laws. This would be the closest thing to moral absolutes for atheists. However, since the legal system changes the morals in a society can still change and their morals along with it. At best, these codified morals are "temporary absolutes." In one century abortion is wrong. In another, it is right. So, if we ask if it is or isn't it right, the atheist can only tell us his opinion.
If there is a God, killing the unborn is wrong. If there is no God, then who cares? If it serves the best interest of society and the individual, then kill. This can be likened to something I call, "experimental ethics." In other words, whatever works best is right. Society experiments with ethical behavior to determine which set of rules works best for it. Hopefully, these experiments lead to better and better moral behavior. But, as we see by looking into society, this isn't the case: crime is on the rise.
There are potential dangers in this kind of self-established/experimental ethical system. If a totalitarian political system is instituted and a mandate is issued to kill all dissenters, or Christians, or mentally ill, what is to prevent the atheist from joining forces with the majority system and support the killings? It serves his self-interests, so why not? Morality becomes a standard of convenience, not absolutes.
But, to be fair, just because someone has an absolute ethical system based on the Bible, there is no guarantee that he will not also join forces in doing what is wrong. People are often very inconsistent. But the issue here is the basis of moral beliefs and how they affect behavior. That is why belief systems are so important and absolutes are so necessary. If morals are relative, then behavior will be too. That can be dangerous if everyone starts doing right in his own eyes. A boat adrift without an anchor will eventual crash into the rocks.
The Bible teaches love, patience, and seeking the welfare of others even when it might harm the Christian. In contrast, the atheists' presuppositions must be constantly changing, and subjective and does not demand love, patience, and the welfare of others. Instead, since the great majority of atheists are evolutionists, their morality, like evolution is the product of purely natural and random processes that become self serving.
Basically, the atheist cannot claim any moral absolutes at all. To an atheist, ethics must be variable and evolving. This could be good or bad. But, given human nature being what it is, I'll opt for the moral absolutes -- based on God's word -- and not on the subjective and changing morals that atheism offers.