The US doesn't actively use large parts of Montana. Doesn't mean Canada can have it. The Quarians were trying to annex Citadel territory. Responding with force is reasonable.
Actually, Ekuna was discovered by the Quarians. Development firms moved in as they were setting up their own pilot colony, and when they went to the Council to have the world they discovered recognized as a Quarian world, the Council's response was to drive them away at gunpoint. It was not Council territory - the Phoenix Massing was a part of the Terminus Systems, and no territory is recognized as Council jurisdiction until the local inhabitants (in this case, the Quarians themselves) recognize it as such.
Wouldn't it have been safer to divide the Quarian population up and dump them in several different systems? Smaller encampments like that would probably attract less attention. They're just lucky the Reapers evidently didn't think it was worth their time to bombard them after the fleet had dropped them off and left.
I get why the Quarians would want to attack the Geth, they've served the Reapers in the past and even if it was unwillingly, the way the Geth operate would make it possible for the Reapers to control them in their entirety. It just seems to me that Rannoch isn't any better a place to leave their people than any other, less conspicuous planet. I mean, they've got enviro-suits, they're better suited than any other species to bunker down anywhere if they're left with ample supplies, aren't they?
Not exactly. They never had "ample supplies" to begin with, being stuck in what the codex called a perpetual state of hand-to-mouth. Their fleet relied on external infrastructure to survive (not prospering, not getting better, but
surviving) even before the Reapers turned up - they lack the capacity to manufacture many of the things their fleet needed to keep going.
Furthermore, read the codex entry on Rannoch. Quarian physiology is such that they need to interact with their native plant life for their immune systems to function properly - as much as they bear a physical resemblance, they aren't human, and have their own specific needs ("Our bodies carried the seeds which spread the desert grass"). As Tali explains at length in ME2, settling on another world and eliminating their dependency on their suits would require a long process of bioengineering. Removing their dependency on their native plant life would require genetic modification - the kind which is both outlawed by the Council and, in all likelihood, unavailable in the aftermath of the Reaper war. Think of the difficulties of "scripting" a human being with no dependency on an external source of vitamin C to get some idea of the challenge that would be.
Rannoch is their single best shot for long-term survival as a species in the event that their fleet does not survive to come back for them - a very real possibility against Reapers. It's literally the only planet in the galaxy where taking the mask off and drawing in a lungful of unfiltered air won't kill them. They won't last long if they're all dumped off on some airless moon (or moons), especially with the relays gone.
I'll have to dig up Han's earlier post and address it, too, when I get a chance.