Networked AI is the important part. The basis of each geth program is software only. Not hardware and soft ware like EDI the only True AI in the game series. Each geth unit was created to perform a simple task. They had the same level of intelligence as a Roomba does. Quarians found by connecting them to each other though wireless network they could increase the complexity of the tasks the geth could do thanks to the increased processing power.
This is the exact same basis of Folding@home. You download the soft ware that links your computer to a computer network that combines your and all other connected computers into a giant super computer capable of doing trillions and trillions of calculations thanks to all the individual computers sharing their processing power.
Eventually enough geth were linked together until they gained enough processing power to gain sentence. That is why each mobile platform holds hundreds of geth not 1. Why Legion containing over 1,000 geth units is so impressive. Why they consider themselves 1 being rather then individuals. Each geth is no more a sentient AI then my inspiron laptop is.
After Legion was upgraded with the Reaper code he gained true AI status. Legion gained a sense of self. Much like EDI has a sense of self and doesn't consider herself part of a collective. Every interaction with Legion in ME3 was after the Reapers upgraded him.
Actually you can because if you grew up in USA and you are introduced into lets say a family that very heavily follows their native Indian traditions. For best learning experience get on a plane and land in any place besides major tourist area in China, India, Japan, South Korea, Vietnam. Culture, behavior, habits are all vastly different from what you would be use to in the USA. While not the perfect analogy for the set up the example that sets is fairly fitting.
Again you bypass the specific reasons he opposes the old machines. Because the old machines would see them create the future for the geth while they wanted to forge their own future. He even then specifically quotes what Sovereign said to Sheapard about the Reapers dictating how society would evolve though the use of their technology.
You have never been in a life or death situation have you? If your live is on the line and you had to sacrifice and arm and a leg to live you would do it in a heart beat. If you promoted peace and brotherly love all your life and then you were put in a position were the only way out alive is to kill your attacker you would kill them. Self preservation is the cornerstone of any life that has any degree of self awareness.
Or lets put it this way picture you sitting at home with your parents and 4 siblings. Then suddenly some people burst into the house shoots and kills your parents and 4 siblings. This causes your over all intelligence to drop and you are aware of the drop. There is no way for you to fight back they are stronger then you are, more well armed then you are and any attempt of direct confrontation would just end in your death. Then suddenly at the window is a man offering to drive them off. To save you from death but in return you had to sell drugs for him. Even though you were against drugs your entire life.
You would take his offer. The fear the sheer instinct to survive would kick in and you would take his offer in a heart beat.
Any alternative is better then death.
Only once the danger was past. Once the Quarians were pushed back. Once the geth were out of Reaper control were they able to see how bad that choice actually was. To realize how easily the Reapers tricked them. Thus their willingness unless you let the Quarians wipe them out to join you to push back against the Reapers.
There is no contradiction in their action.
The Reapers use organic or inorganic means to attack. All those husks, cannibals, banshees, brutes and marauders you face in the game are organic beings. The Reapers use every possible source to assist them in their harvest. Geth would be used the exact same way a husk would be used and treated the same way afterwards.
Quarians wouldn't have stopped anything forever. They would have stopped it for the time being but you can never stop it forever. No more then you can stop drug use forever or stop terrorism for ever or any number of things that can and will always happen.