"...absurd practices [such as] Nazi euthanasia or American eugenics..."
I'm quite shocked that you put age discrimination - which is, I'm assuming, what we're still talking about - on what appears to be equal footing with either of these particular examples. In this case, such a practice doesn't have nearly the same "logical conclusions" as Nazi exterminations (I'm surprised you use the word euthanasia). After all, we're not talking about establishing a "Logan's Run" society here. For example, suppose we, as a society, were to establish the practice of prohibiting anyone over the age of say, 50, from participating in a particular event or job (with the consensus that such a practice has been deemed to be for the common good). To me this is not much different from the traditional taboo/stigma associated with incest, for example. We have not sought to supress such a practice because it is inherently evil, but rather because it has severe biological risks to the species, i.e. not beneficial. And notice also that age discrimination is fundamentally different from excluding a particular race or sex. One cannot change one's race or
sex <- (i know, i know). However, since on average EVERYONE can be expected to live to at least 50, they too will be subject to the same law, which in fact ceases to be discriminatin as a result.
Finally, let me point out that we do not have a difference in philosophy since I do not believe I've EXPRESSLY advocated the establishment of such practices. My original post's intent was to stimulate some interesting point-counterpoint and I hope I've done that...
PS
I think that "waiting to get married and have children" situation also raises some interesting points that would make for a good thread...