Committing genocide against the Kett is a must?

You know I'm a very nice guy, so I'll let them choose their own future.

If they stand in my way, their anuses shall be destroyed... Otherwise, Live and Let Live

Yeah, it seems our penchant for rampant stupidity bleeds over into the human-like aliens as well. 

Needless to say, I found the Rachni's willingness to help and not ask for any handouts to be far more appealing than the Krogan's overall victim mentality. But that's just me.

Not necessary, what you are describing is a requirement for progress. Otherwise they wouldn't be able to invent stuff, because eventually they would reach invalid conclusion without any possible alternatives.

I understood it more in a way that original heretics arrived at the conclusion of worshipping the reapers without outside aid and were allowed to leave by the true geth. Hovewer later heretics decided they are so right nobody can disagree with them, so they designed virus that would slightly corrupt processes of the true geth so they would conclude reapers = awesome.
And then of course based on your choices Legion might redesign that virus so it works the other way.

Question: if milky way races number in about a million at most, how are you gonna destroy a race that has the population in the billions?

Besides we dont even knwo if their homeworld is even in the Heleus cluster, it could be far away.

You reminded me of this scene from an old anime (Arislan Senki):



"How many of us are there?"
"Including you, six."
"Our fighting strength has increased by 50%."
"The Lusitanian army is 300,000 strong, so we're down to 50,000 each."
"Oh, great."
 

You could always just park outside their systems and sling dino killers down their gravity well.

What does Dark Space have to do with anything?  Dark Space appears to be part of the MW, just a part where there are no stars and planets.  Even if it's outside of MW, the planets and stars in the Andromeda Galaxy still don't fit the definition of Dark Space.

We're talking about Bioware here.

Besides, the Geth may just be software, but they are still a sentient AI when linked together. They themselves aren't even completely aware of what that entails. Remember asking Legion about the integrated piece of Shepard's N7 armor and he returns "No data available."?

Is it so hard to accept that different Geth might come to different conclusions regarding the future of their species? This was a crucial choice with massive repercussions, either follow the "perfect" machines or build their own future. This isn't some simple math equation that will always result in one right answer. By saying that it takes a virus to make any Geth consider joining the reapers, you're robbing them of any sort of agency. Remember that in ME3 they willingly joined the Reapers to avoid their own destruction at the hands of the Quarians (although that was a lazy retcon to create a big conflict for the player to solve).

Got it.  Makes sense.  And accurate, most likely, even if we're relatively friendly.