My Views On This:

I can see the Doctor's reluctance at genocide, having experienced/will have experienced it firsthand in the future, seeing millions and billions of lives destroyed and ruined, he doesn't want to stoop to the level of the bastardly, dastardly Daleks. You yourself would fear to become father who hits your own child when you received the same treatment in your early years, you would recoil and be appalled at what you did or almost did.

From what we see in the New Who-era of Eccleston, Tennant, Smith, and Capaldi, they have gone through the Time War and 'seen' Gallifrey and the Daleks 'burn', he has that in his conscience, the sheer weight of the deed and he never wants that to happen again (which he can prevent by killing all the Daleks, but more of that laterrr), he became more peace-keeping and an advocate of non-violence confrontations to a higher degree because of his experience.

The morality of killing them all, to stoop to the level of a Dalek, killing machines without remorse traveling through the cosmos killing millions of lifeforms, his most dedicated and formidable enemy, it simply won't do. He won't have him being compared to a machine devoid of emotions committing genocide even if it's for a noble cause (which is of an abstract concept depending from person to person and is relative to societies and so on and so forth, which I will explain in a later date, and not here). To the Daleks, the extermination of all life that is not Dalek is their most noble and central goal, to the Doctor the saving and preventing of deaths and all things bad is noble to him, but not to others, etc etc, it's very relative.

BUT! To the main body of this argument/opinion/thing is that if the Doctor touched the two wired and destroyed the incubating room therefore destroying the Dalek race forever, he would have saved multiple planets, billions and even trillions of lives throughout the Universe, the Last Great Time War would never have happened, Gallifrey would still be there. But as he said "You see, some things could be better with the Daleks. Many future worlds will become allies just because of their fear of the Daleks." and indeed many good things would sprout from the evil of their abominable race, alliances formed, friendships strengthened, technology developed for the greater good etc etc, which is all very similar to the famous argument "What would happen if WWII didn't happen?". He does not want to change the future for fear of fucking it up in the process, things could very well change, the Daleks could be replaced with an even more bastardly race of super Nazis. It is possible that he wants  this timeline/Universe to stay as it is because he knows what the future is, what kind of destruction it will bring and there's a kind of certainty, like would you rather have a toy that you're absolutely sure will be like the toy you want, or would you rather have a Kinder Surprise and a random toy, you won't know if it will be shit or if it will be good. You obviously play safe and pick the badass 11th Doctor Sonic Screwdriver and not the blind-bag pack.

Aaaand, he could see a spark, perhaps a vision of them doing good, he's giving them a second chance,  he doesn't want to kill them all and then it turns out "Whoops! Turns out in the 420th century they help the Humans in their habitation problems blah blah blah" He wants to know if there is a possibility of them being nice (Which, if you've watched enough Who you'd know is complete bullocks). 

In my honest opinion, he should've killed all these buggers, would've saved him lotsa time and effort, lotsa lives and planets and collateral damage and emotional trauma. It would've been a better world without them but the same could also be said of humans being gone from the 21st century, with all our pollution and making animals extinct and all.

"The end justifies the means." Says Niccolo Machiavelli, which in this case is peace throughout the Universe. If you have a strong sense of conviction or an ideology that is not confined to that of society, then this action could've been carried out smoothly. 

WHAT DO YOU GUYS THINK?

Genocide or GeNOcide?

COMMENT DOWN BELOW :)