Any proof for this? Because I don't remember any.
What do you think would have happened if Tali took off her mask and breathed deep on, say, Omega?
What? How do you come to this conclusion?
ME3 codex entry on Rannoch (physiological dependency on native plant life), ME2 discussion on Quarian immune systems (same), ME2 discussion at the console asking why they haven't colonized another planet. That "60 years or 600" is a direct quote. Add to that the ME1 codex on genetic modification: enhancing natural abilities is legal, "adding a tail or the ability to digest cellulose" is not. Modifications to remove their dependency on plants they no longer have access to seems to fall into the latter category. It'd be like scripting a human who didn't need vitamin C.
I'm not saying that there is no benifit in being armed. I'm saying that maneuvering your civilian ships deep into enemy territory where they'll most likely end under fire is one of the most supid military strategies I've ever heard. Bonus points for flying your entire race into a firefight, so that your entire race can be wiped out.
It's not like they wanted to. Split the fleet and you both reduce its firepower (meaning it'll take longer to get the job done before they can offload and commit to the Reapers) and throw a wrench in logistics. Xen, at the start of the rescue mission: "Even Koris recognized the need for the civilian fleet. The invasion would be stalled without a supply chain, after all."
And their plan can lead to the extinction of their entire race in the game. If a plan can lead to that, it is by default a incredibly stupid plan. Also they knew that the Reapers were around and that some Geth allied with them in the past. The admirality should have probably taken that into some sort of consideration before leading their entire race (Those dumb*sses even called back everyone that was on their pilgrimage or otherwise away from the fleet) into war agianst the Geth.
I guess they should have sacrificed a goat and read the entrails to discern that the Geth would run to the Reapers and receive code upgrades that even the heretics never had? Any military engagement is a risk. In this case, using Xen's flashbang was deemed less risky than clumping around in space, incapable of offering aid to the other species and waiting to get picked off. And as far as risking extinction goes, could say much the same about throwing all of our resources into building... something... that we don't know what it does in hopes that it might beat the Reapers.