I commented over at The Reason Behind X:
Thanks for taking the trouble to comment on this. As you'll have seen, I take a fairly robust view on this. I.e., I don't look for responsibility all the way down.
There may be extra strands to the story, but I think that the starting point is that we find such traits as intelligence, courage, honesty, etc., admirable, while we find such traits as stupidity, cowardice, dishonesty, etc., the opposite. Generally speaking that's rational, as someone with the former traits will usually be better to have around as a friend, fellow citizen, etc.
We don't generally care all that much how someone got these various traits, though we might admire someone more if we find out that she got the admirable ones partly through pre-existing good traits like self-discipline, industriousness, etc. But even those traits have a causal origin that's ultimately beyond her power.
Likewise, there might be some mitigation of our disdain if there's a special story about how someone came to have the contemptible traits - they can't be blamed on some pre-existent bad traits she had, such as some sort of laxity or laziness, so much as some unusual external influence that might have made her turn out that way even if she started with normal levels of self-discipline and so on.