They should not deny that they killed about 1 million Armenians but I would not call it a genocide to be honest. It is a matter of definitions but the word genocide is being overused for almost anything these days.
The Armenians were in an armed rebellion against the Ottoman Empire and cooperating with the Russians in what we can call a war of liberation. The Turks who carried out the killings were mostly irregulars and it seems that the central government attempted to restrict the amount of killings by deporting Armenians from the sensitive areas to the historical Armenian homeland. One has to understand that Armenians were living throughout Anatolia in the early 20th century due to centuries of wars and events.
The term genocide was coined after the holocaust and thus, when one wants to use the term, he evidently has to compare the event in question to the holocaust. For the Armenian "genocide" to be a genocide, you would have to assume that when Adolf Hitler started killing the Jews and issued the Final Solution, the Ashkenazi Jews of Germany had been in an armed revolt for years, trying to assist the English, Americans, and Russians against Germany. Then, you would need the crimes to be committed by irregulars rather than by regular troops and the government. Also, you would need the Nazi government to deport Jews from the sensitive areas to a safe harbor (Palestine, let's say for the sake of argument) rather than to concentration and death camps.
Ultimately, the massacres of the Armenians during WW1 was a terrible event and the Turks should certainly apologize for it. However, it was definitely not a genocide if definitions matter.