I blame the intolerance of Christians.
Well really, the Ottomans DID NOT go out of their way to kill every Armenian they saw. The Armenians decided to go full-out revolt mode, and threatened the fall of the Ottoman Empire.....to the Russian Army. I can understand that the only solution without resorting to genocide would be to migrate them away from the frontlines, negotiate, or promise independence/extreme autonomy. I believe the Ottomans tried all 3, but the Armenians refused to listen and demanded an Armenia stretching from Central Anatolia to Persia. I don't blame the Ottomans for going with option 1, the only one that seemed possible, as Armenians refused to cooperate , seeing as they tried everything, but the Armenians where on a nationalistic no-talk sentiment. What I DO blame the Ottomans for is poor, horribly poor, and in some cases downright horrible way they managed the movement of Armenians away from the frontilines after promising them extreme autonomy, if not outright independence, on a provincial majority basis. In some cases disgruntled Ottoman troops mowed down Armenians that refused to leave or attacked them. That, is when the Ottomans move from having my slight sympathy, to downright disgust. Armenia should have become independent, but not the outrageous demands that they wanted unilaterally. It's like giving Serbia Yugoslavia, Albania, most of Hungary, Bulgaria, and Romania. Insane overkill.
So in summary, I blame the Armenians themselves, as well as the Ottomans. The Ottomans even had the title, 'The Most Loyal Subjects' for Armenians; that should show how much of a stab in the back it was when Armenians revolted.
Does this come off as me defending the Genocide? If it does, I'm sorry. It was a horrible, horrible thing, that to this day is still something that must be studied and all efforts made for something like this to never happen again. But honestly, I think the Russians killed as many Armenians as the Ottomans, in terms of Armenians and Russified Armenians during the reign of the USSR, except they most likely hid these records, if there ever where any records of it. Meanwhile, the Genocide is BARELY known in the West, and everybody assumes it was a Hitleresque genocide full of hatred, bigotry, and killing on purpose. It wasn't that. It was a poorly managed relocation(which is plenty bad enough). But I still hold that the Armenians are also to blame and it can't be viewed through bias, despite the Ottomans receiving almost all of the blame IMO.