I did not mean to imply that anyone who will not change their minds after a debate are doing this. I was merely talking about those occasions when this actually becomes evident like you said.
I should have been more precise, but yeah. And using Christianity in my post was just an example drawn from recent experience. My post was not about any ideology in particular.
Oh, and sorry for keeping this off-topic stuff on, but I realized to demonstrate what I was talking about, I could now instead of saying that you were right and redefine my allegation, I could have said "but when they don't change their mind the discussion has to go on and we waste more time." Thus changing my argumentation completely while ignoring the fact that you just logically proved me wrong and I am now discussing something else.
Well, I still don't know that it's ever evident, and I certainly wouldn't have thought your latter example outside of the scope of the original debate. In any event, while subjects for debate perhaps require some limitations, I think you should be careful that you are not, in defining the parameters of your debate, structurally privileging arguments that are supportive of your position.
For instance, assuming that in your original example the subject of the debate was the existence of God, I do not see that raising the issue of whether religion performs good in the world is necessarily irrelevant to the original question.
In that I mean it is a perfectly logical argument to say that, if God does not exist, there is no value to human life; absent some divinity, each individual person is worthless - you are simply one speck of dust among seven billion on a tiny planet in a vast and incalculable universe. Your life will be cosmically brief and will likely leave an impact so minimal that not even your great grandson will remember your name. Even if you are one of the rare individuals whose life is remembered by history, such a memorial affects only people whose lives have no more intrinsic meaning than your own, and it certainly doesn't affect you, because you're dead. Arguably, that basic thread of logic is a premise of the Abrahamic religions, with some of the first words in the bible describing life after Eden as "you are dust, and unto dust you shall return." (that line of thought is more fleshed out in Ecclesiastes).
To my mind, that argument is not unrelated to the question of God's existence, since it goes toward the very reason for the hypothesis of God - that is to say, His existence validates the sense of self-worth and altruism that is arguably innate to all human beings. Is it not an unfair constraint to debate a hypothesis without permitting your opponent to advance any observations which form the basis for the hypothesis? To debate gravity and refuse to permit the observation that objects fall down and not up?
Given that rationale, the question of whether religion does good in the world
is potentially relevant to the question of whether God or some divinity exists, since it could circumstantially validate the hypothesis outlined above.
I truncated that argument since it was only an example, but my point is only this: if you construct the subject of debate too narrowly, you risk introducing a bias toward your own position, especially where the onus of proof is on your opponent, as it would be on the person arguing the existence of God. It seems to me a narrow debate indeed if you forbid your opponent to raise reasons for his or her belief. If your objective is truth, I would advise against building artificial walls that disadvantage those who do not share your opinion.