It seems rather awful to me that conscientious objection (CO) can only be made on the basis of religion. Like, you can stop killing people if a new understanding of the almighty has led you to believe that there will be divine retribution if you continue in your current military capacity, but if you have come to the realization that the actions you're engaged in are immoral on a fundamental, human level, you're going to have to keep doing it?
The psychological repercussions alone are formidable, and PTSD and other psychological disorders are already hitting extreme highs in veterans coming back from war. I understand the need for discipline and order in the military, but mental health is important and the army ought to be caring for its soldiers. This is admittedly an oversimplification, but killing people is bad enough, for various reasons, but in this context in the sense of damaging a soldier's mental health. Ostensibly, they came to the army with a general understanding of what they'd be doing; however, if they come to feel that they are committing a terrible injustice and literally aren't allowed to stop, that could cause major problems later on.
And as for the argument that if COs can be made on nonreligious grounds everyone will do it, consider this: if there is that much ill-will towards a war, that soldiers are using any method possible to flee it (which happens not to even be the case), then perhaps that war should be reconsidered. Obviously military decisions cannot be entirely based on popular opinion, but if a volunteer army means anything, it means keeping public and military support high enough that this isn't a problem. It's a ridiculous argument anyway; how do you prove that someone has 'actually' converted? That gets into another whole set of issues about what it means to be religious.
Finally, there's the idea that this is a manifestation of a prevalent problem: that religion is given a measure of respect accorded to no other ideological system. The Christian behest not to kill is not more powerful or better than a secular empathy, a knowledge that killing is as harmful to others (the victim as well as those close to them) as it would be to one's self. In fact, I would argue the other way around, but that's a separate post. And for the record, the vast majority of American soldiers are Christian, so the very notion of religious ethics being somehow more imperative is moot. Also, let's talk about that idea for a second. Firstly, secular ethics are only less controlling in the sense that they are not dogmatically forced on people, and they are subject to change given new evidence. That does not mean that people who follow nonreligious ethical systems are flighty or capricious in their moral dealings. In fact, they are likely to be more thoughtful about them, given that there is no book to which they can turn for every conceivable situation. Secondly, those characteristics are positive ones, and should be encouraged. I worry for people who decide that murder is wrong because someone else says that god said so. I'm well aware that religious ethics are not even close to this simple, and that not all secularists think deeply about the philosophical ramifications of their actions. Nonetheless, realizing upon consideration of the evidence around you that what you are doing is wrong is a mature response, and should be accepted and promoted.
Basic point: in a volunteer army fighting for liberty and freedom, there has to be some leeway for conscientious objections made on nonreligious grounds, for the sake of ideological consistency, care for the mental health of the soldier, and a realization that philosophical affiliation can be just as important as religious affiliation, and secular ethics are no less valid than religious ones.