So it seems to stealing blood is their bounden duty, and they seem do not have enough free wills to refuse it; hence this action looks more unmoral than immoral.

I believe that you have already given the very correct answer to your own question: It is not immoral.

So it seems to stealing blood is their bounden duty, and they seem do not have enough free wills to refuse it; hence this action looks more anmoral than immoral.

I believe that you have already given the very correct answer to your own question: It is not immoral.