Look, I think it’s a waste of time to try and convince anyone that their religious indulgence is silly and potentially harmful. It’s not based on rational thought but rather rationalizations to silence the doubts and the conscience in order to keep indulging, so logic probably won’t work. You could pull the same trickery they use, and probably be more successful but, to me, that’s rather shady and you really haven’t changed anything since if the basis of one’s belief is emotional or some similar crap, then that’s not a solid foundation so they could easily shift back or to something else that’s bad or even worse. I find there are three reasons for engaging in arguments with the religious and evangelists of irrational beliefs, and that’s to disarm, to educate, and for self satisfaction.
Since we know the religious use any means to get their ends, dismantling their arguments can help to get rid of some of their means. Sure, they still use them, like Pascal’s Wager, but it’s also easy to dismiss publicly as well because the argument has been so thoroughly dismantled that the dismantling is common knowledge to the rational. I know some poo-poo the idea of atheists reading atheists books in which arguments are dismantled, suggesting that they’re merely books to embolden the faith of atheists, but I think it’s a mistake to assume every atheist is a wildly intelligent person well versed in logic. Look, religious arguments can be very challenging and obviously work very well to convince people. They’ve been designed and modified over millennias. The initial dismissal of a god claim can be simple enough for a child to do, since refusing a claim for lack of evidence can’t get much simpler, but the religious have cooked up some rather devious tricks to get you to believe, so even though you know what they’re saying is a con of some sorts, you may not be either smart enough or educated enough to see through it and dismantle it yourself so having resources out there where the work has already been done is something I see as a good thing.
Now obviously having these dismantlings out there publicly addresses my second reason for arguing, but also I’ve always thought that debates are really for the onlookers, because you most likely can’t change the mind of the religious person you’re arguing with. They possibly have had a lifetime of both being fed outrageous rationalizations and emotional appeals to believe as well as ample experience cooking up their own more personal ways of maintaining belief, so a dismantling of their arguments as well as some clear, rational arguments of your own probably won’t undo all of what they’ve got going on in their head to safeguard their indulgence. However, who knows what state the minds of the onlookers are in? They could be convinced, or at least have some failings occur in their indulgence protection grid, and that could have a cascading effect. And again, the exercise could also serve to educate those who knew the religious arguments were just a con but couldn’t work it out on their own what the trick was.
The third point can be taken many ways. You could gain self satisfaction by believing you’re helping others by killing these arguments. You might gain pleasure by believing you are in fact taking some means away from these people to push their snake oil. You might want to flaunt your intellectual muscle. You might be a recent deconvert and doing this is cathartic, allowing you an outlet for the anger and shame of having bought into this nonsense for so long. Ultimately, I believe all of our actions eventually boil down to acts of self satisfaction anyway, so regardless of the why, if you take the time to argue with and dismantle the arguments of the religious and pushers of similar nonsense, you’re doing so for some for of self satisfaction.
But why do they do it? That’s something for a post of its own probably, but I’d say it’s mostly due to wanting to spread their belief to others, and to bolster their own faith in the belief. In the case of religions, there’s the added incentive of making a show of being a good believer, which may have rewards now but the rewards they’re primarily after are the ones they believe they’ll eventually receive after they die.