That is irrelevant because they were still under the influence of demons. So putting the blame on them it is still wrong, no matter how you try to twist it.
Not to mention that in war 3 they were tricked into drinking the blood, Mannoroth put it in a fountain of life and in WoD they were desperate because they were losing in every front. So neither of those situations really aply as willingly, since one they were tricked and the other they were driven by desperation.