The person I responded to was saying they didn't care about the future of the species.

I was replying that we, as a society, DO care about the future of the species. We put laws in place to help further it's survival, mostly around supporting the currently existing children (tax breaks, education, etc), but also around helping people have more children (FMLA).

The reason those laws exist really isn't that different from the laws that support property rights; they support things we, as a society, value.