How do you decide whether it's worth arguing with a religious person? Do you take their psychological fragility into account? I definitely do. Sometimes, 'tis best to leave someone's tin foil hat, the one protecting them from the deadly space rays, firmly in place.
If there's an audience, I jumpo right in, no matter what, in hopes I can convince some of them. If the person is the standard "I don't care how much evidence you show me: I KNOW I'm right," I don't bother. There's far more productive things to do, like finding out where to get McDonald's Mulan Szechuan sauce.
Why argue? Does anyone gain anything in the argument? Ultimately, it wastes everyone’s time and accomplished nothing. On the other hand, conversation and debate give an opportunity to discuss and air ideas and viewpoints. I hate to argue, even on a personal level.
Why would I presume to do it? They have something in their lives that brings them comfort and gives them a sense of purpose. What gives me the right to take that away from them?
I have no issue with people taking comfort in the belief in an afterlife, or in a benevolent god who will look upon them favourably and give them hope when their situation seems hopeless. My issues are with the bigotry, hypocrisy and greed practised at much higher levels within organised religion. The Catholic church hoarding wealth and denying its child sexual abuse issues. Billy Graham dying worth $25m, every penny probably taken from someone significantly financially worse off.
I only take exception with religious individuals when they try to dictate that I should live my life by their religion's rules. So the bigot standing there with the placard saying that all 'fags' and 'fornicators' are going to hell? I'll happily tell him how ridiculous his 'mysterious sky fairy' belief system is.
I used to skip any argument but for some reason lately I've been leaving comments on religious posts on my Facebook page from the feeds of friends. I usually give a paragraph saying there's actually no god, mention the Sumerian texts and explain how the Hebrew god is really copied from "Anu" the Sumerian leader, leave a link to info on it.
I don't expect a response, just leaving a hint for them to extricate themselves from that Christianity lie, if they are so inclined. My attitude is that if they defriend me, I couldn't care less.
Yeah, sometimes I back slowly away and leave them to their insanity. Sort of like when you meet a mutterer on the street and tell yourself "don't ... make ... eye ... contact."
In fact in real life that's mostly what I do, on those rare occasions when someone is clueless enough to even broach religion or politics in otherwise polite conversation. I don't live in the Bible Belt, after all.
Online, debate is occasionally good sport, although I find I really neede this online community which is fairly theist-free. It gets tiresome, and as others have suggested, is something of a dead-end street. The only reason I still do it somewhat on other sites is that there's this rule that says that for every active poster there are as many as 99 lurkers and I do it for them. I used to be a lurker, unable to admit to myself, much less others, that I had grave doubts about my theism. I try to post the sort of content I wish had been there for me, when I was on my way out the door of theism.
I believed because I honestly thought it was true. When learned the facts and heard reasonable arguments, I stopped believing. I'll engage with any believer at least once because I know there's others who are just ignorant like I was. They're worth it.