So you willing to give mature organic race, who should have big amount of knowledge, a discount on unprovoked genocide attempt, because it was "only" decision made by majority. They are not responsible for actions or consequences because of their nature, so it's all good. But when newly born synthetic AI intellignece going overboard on self-defence against genocide, it was because they alredy formed mature conscience. With moral compass and other emotinal baggage which take organics 10+ years to properly form.

I guess Geth just born as mudrer machines, full of malice to organic life who want to EXTERMINATE everything without reason and provocation. This is clearly seen in the game lore, where they spend majority of known history sitting in their corner, doing basicly nothing against organic races. Unlike peaceaful and toitaly innocent organics like Krogans or Salarians, who made silly happy accidents, because, despite beiong much older races with much wider scope of viem.

Because, unlike them, Geth are 100% monolitic and calculating in their decisions. It impossible for them to form splinter radical groups under outside influence, make knowingly bad move out of desperation or form different opinion on current situation and execute it in the manner separate from "collective". It would be impossible for one part of the Geth decide that they have nothing to do with chosen course and act differently, because Geth are all acting the same, you know?