In debate with theistic advocates, it isn't hard to seek out their strategy. In defense of a being whose existence is, at the least, highly dubious that resides outside the normal rules of fact-finding, the tactic most used is to take something that most humans deem desirable and allow God to monopolize it.
It's pretty obvious that these things are: ethics, meaning, and cosmic purpose. The theist side assumes the existence of objective morality / intrinsic value, objective meaning, and cosmic purpose. Their scope is so limited that they can't perceive anything from a non-anthropic perspective, but let's ignore that for now. I believe it is a mistake to acknowledge the proposition that these attributes of the universe are desirable in the first place, thus ceding the "high ground," so to speak. I have seen in debates (most notably with William Lane Craig) where an atheist may play the game on the religious apologist's terms. By ceding this high ground, the audience or potential "convert" will wind up being more sympathetic to the apologist's emotional argumentation.
Put differently, instead of claiming, "yes, those things are nice but here's why I believe they don't exist," atheists could make more headway in obliterating the very idea that these are nice things. Let's begin:
1. Objective Theistic Morality
First things first, theists say that in order to claim God is tyrannical, one must allow for the fact that good and evil exist and the only way that can exist is with a higher authority than man. They never substantiate this claim, it is just made with no justification. Why can't man's opinion be the highest form of value judgments? Why do we need a celestial babysitter to declare that one action needs punishment and the other reinforcement?
I, for one, am not a moral realist in the sense that moral "facts" aren't really facts, but in no way does moral anti-realism (which doesn't deny some type of modified code in human behavior) follow from atheism. There are many defensible forms of atheistic morality, like Ideal Observer or Natural Law. Now many prominent atheist philosophers such as Nietzsche (who I'm closest to) or Camus or Sartre had their objections and were anti-realists in some form or another, but their positions need to be argued for or against and are in no way a given.
Secondly, referencing the main point of this piece, what is so great about having God tell us what is good and what is bad? The way this system is set up, it is supposedly objectively good to send the majority of humanity to rot in Hell. There's no way to appeal this sentencing and God has coerced you to belong in his system. At least with competing human moralities, there is some sort of cooperation and compromise so that the least amount of damage is done to each party. After all, according to Divine Command Theory, what we have is a being who promulgates something as being good irrespective of our opinions. A good example is placing prohibitions on human sexuality. If it makes us less happy and more uncomfortable, what is the point of morality? It ceases to serve us with any utility. At this stage, morality becomes a control mechanism. God can punish moderated envy, moderated lust, and moderated anger, all of which are important to individual health, for no other reason than merely classifying it as evil. The good/evil dichotomy is where religion has distorted our intentions regarding behavior. Instead of a dialectic of good/bad, desirable/undesirable, or smart/misguided, this system promotes an ultimate "us vs. them" mentality without really having to give a justification for why something is good and why something is evil. Instead of thinking critically about why things are to be applauded or avoided, God's authority stems from being a presupposed archon whose authority is not earned, and thus not evaluated reasonably and manifests itself as internalized fear. This separates our desires from our goals, and that causes emotional frustration.
So in a nutshell, what humans really want is freedom to overcome their limitations and seek desired ends in a reasonable manner that takes into consideration the abilities of others so that we aren't raging psychopaths, because that is our nature inherited from evolution. What the theist in this argument wants to do is coerce you into an all-or-nothing system. "You can't have that if you don't accept all the other baggage that our God provides, and if you don't like the baggage, that means you are rebelling against God." It's a very clever device, but one that we need not fall into.
2. Objective Meaning
The argument concerning life's meaning is another religious creation that offers an inflexible, all-or-nothing trade-off. As I believe Peter Atkins once put it, "theologians really make a living out of inventing questions and then denying that science can answer them." Either you accept Yahweh's plan for you to understand him, or you have to contemplate suicide and you may as well kill yourself since you have no meaning in life.
Again, is Yahweh's plan for us something that is desirable? Theists, again, make an interesting case that if you don't know Yahweh, then you can't experience how fulfilling his plan really is. So basically, "if you can convince yourself Yahweh exists and you convince yourself how fantastic his plan for you is, then you can fully appreciate his plan for you. And if you don't understand or appreciate his plan, then you're not trying hard enough." Again, more ham-handed reasoning.
Yahweh acts as a celestial dictator who coerces people into situations that they do not approve of for reasons they don't understand. I'm sorry, I don't like that system. His "meaning" is not my "meaning." If meaning in this sense is what we strive for, what we live for, and what we enjoy, then we have many sources for meaning. We humans can create our own meaning. This meaning may have its origins in many facets of life such as struggle against insurmountable odds, happiness, helping others for the apparent sake of helping others, etc. It is many things to many people. Human-created meaning need not be a one-size-fits-all solution as it can vary from individual to individual. Two secular thinkers who helped articulate this are the philosophically (somewhat) opposed Socrates and Nietzsche when they stated, "Know thyself" and "Become what you are" respectively. I don't know if better commands have been stated, and certainly anything the petty Holy Fuhrer Yahweh has uttered does not come close.
3. Cosmic Purpose
Cosmic purpose is something that can be desirable or undesirable to different people. Some people may feel the need for their lives to be dramatic on a grand scale and others do not. I believe it is a sign of emotional maturity to accept the fact that our lives were not intended, that we are accidents, and that nobody has plotted out what we make of our lives. It also gives us an extraordinary amount of freedom to act out as we wish.
There is no need to assume we are anything greater than what we are; a primate species evolved with the best known capabilities of abstract / logical thought and one of the highest forms of emotional capacity. Why do theists need to expect anything more? And while apologists of many stripes may harp on our lowly origins, as Darwin stated, I fail to see how that effects the human species in the here and now. What matters is not how we came to be, but where we are going. And being capable of explaining how psychological phenomenon can be reduced to neurochemical impulses does not diminish the grandeur of the subjective experience of neurochemical impulses. So I believe the idea of cosmic purpose ties into ideas about the soul and how humans aren't elevated above the other creatures of this planet, at least not in an arbitrary sense.
In conclusion, the offers on the menu presented by theism can be modified by atheists and implemented into our own individual repertoires. We don't need to be told what our meaning in life is, what can make us happy, or how to live a "good" life. What we need is to get in touch with ourselves and actualize lives that we think will accomplish all of these things. The largest failure of religion is to ignore the individuality of the human species and disregard the utter failure of top-down authoritarianism. And why wouldn't it? It is a by-product of the infancy of our species, one that was illiterate, uneducated, mystical, brutish, and fearful.