The point of the previous post may not have been communicated as clearly as I like, so hey, time for me to be blunt: it's hard to feel much concern for a group of people who regard you as a hateful savage that the world is better off without. It doesn't matter if this group exists right now, or will only exist at some point in the future. If they have or will (supposedly) certainly have that attitude towards you, well... putting God aside for a moment, it's hard not to say 'well, screw them'.
I think this very basic and natural human response to large groups of hostile individuals gets obscured because of the nature of talking about future individuals. They're 'our children and our children's children', even if we individually don't have any children. That collective 'we' thing that's so popular. But it's not people's children or their children's children who will inherit whatever world we leave them, because children don't own much of anything. Those *adults* the children will become will inherit the world. In the fever-dreams of the progressives, these are trendy, hopelessly liberal, conservative- and even Christianity-hating people who will actively revile everything that anyone even somewhat socially conservative (namely, yours truly, and quite possibly you the person who is reading this) value.
Yes, this is all meant to be an emotional weapon with which to threaten the socially conservative into changing their views - you know, adhere to the pack mentality to be. 'Gasp, you oppose gay marriage! Everyone will hate you eventually! Or they'll think of you as a primitive savage to be pitied!' But while this may work on some kind of human being, it really seems to me that another, more powerful response is in the running: visceral, intense dislike of future generations in general. Oh, my using more coal will make life tougher for *those assholes*? Well then, turn up the heat if you will. I always wanted to live in a sauna.
Now, that's putting so many things aside. Christian morality, an Aristotilean approach to the good, etc. And I suppose to a certain sort of individual, it all seems so distasteful in general to think that way. Aren't we supposed to be better than that? And according to the aforementioned objective standards, we are. But when we put them aside, there's very little ultimate reason to do that aside from, perhaps, the social and cultural handjobbery to comes with 'being a good person' even when 'good' just means 'doing whatever the whims of the louder parts of the culture happen to be at a given moment', in which case, thank you but no.