Let us not to talk about war so slightly, it is a serious manner and we all are supposed to avoid it...
I get where you're coming from and to an extent I agree, but that doesn't mean we can't talk about such hypothetical stuff.
People talk about stuff like the moon falling or the sun dying and many other hypothetical stuff like that (maybe not on the forum)
Talking about it doesn't mean they don't understand the implications. It doesn't mean they want something like that to happen. It could be that they're just thinking out loud.
No one who has the slightest idea of the impact of a war would wish for WW3. It would be a war where there would be no winners in any way. It would be too disastrous.
I also believe it's by talking about it that a lot of people who have never experienced wars and live in countries that have never had wars have an idea of how disastrous a third world war can be.
It does not necessarily have to do with people coming from countries where they have never had a civil war or a war against other neighbor countries. For example, here in my country we have had civil wars in the distant past, and yet there are people who have a very wrong mindset, mixing nationalism with a bloodthrist politic rethoric.
In the United States there is also people who talk about war and conflict, and we all know the United States is one of the countries which have been more involved in wars (they also had a civil war). The problem is the lack of education amoung the youth, who believe wars are like those they see while playing Call of duty . They believe it is as easily as shooting and taking cover and cannot imagine what is to actually have their life in danger most of the times during a campaign.
On the other hand, perhaps I simply do not like to talk about war, because it gives me the impression we are indeed getting closer to a global conflict, that is something I seriously do not want to live through...