In an earlier post, I commented that one goal many atheists have is to end religion. I'm keenly aware that this is a goal that many object to. One of the stranger objections people make is, "You don't actually think that's an attainable goal, do you?" as if to suggest that we should just give up any effort of any kind. It's a form of concern trolling, advising people on how to accomplish their goals without actually sharing those goals.
I hesitate to label this as a logical fallacy, but it is a peculiar line of reasoning that I see applied in many contexts. Why should we try to eliminate poverty if there will always be poor people? Why try to eliminate war if there will always be war? Why try to eliminate superstition if there will always be superstition?
It's a distracting argument. We could easily get caught up in the issue of just how attainable our goals are. It's quite possible that I really do think the reduction of religion is more attainable than some of my adversaries do. But that's besides the point. The point is that this is black-and-white thinking. Superstition is not an all or nothing thing. Superstition can have different degrees of prevalence. There can be different degrees of disparity between poor and rich. War can be reduced.
If I say, "I would want to end superstition", it's not an attempt to make a black-and-white statement. I'm really saying that the closer in degree we are to ending superstition, the better. I also happen to think that we can get at least a little closer to that goal if we try, but who knows, maybe we can't. Maybe we're just running on a hopelessly fast treadmill. That doesn't mean we should stop running.
There's one situation where the unattainable goal argument might work. I think it could be used, at least at first, against a communist's goal of revolution. The benefits of revolution don't exist until revolution is actually achieved. And with communists being as few as they are, revolution seems like an unattainable goal. But I'm sure a number of objections could be raised (and will be raised in the comments). I could see it argued that revolution is attainable after all, though perhaps after a long sustained effort. Revolution has happened countless times throughout history. I could also see it argued that there is some way to approach revolution by degree, and that the closer the better. My point is that the unattainable goal argument cannot be used to bypass substantive arguments, even if the subject is revolution.
A related argument is to say the end goal is undesirable. If we were to completely eliminate religion, we would have unhealthy levels of uniformity of opinion, and effectively no freedom of religion. I'm actually sympathetic to these arguments, but it's all moot. Complete elimination is unattainable, and in the event it becomes attainable we can reconsider the issue. Right now, the relevant issue is whether small reductions in religion relative to our current state are desirable.