Okay, so when you go to Virmire, you learn that Saren has a cure to the Genophage (the disease that is killing off the Krogan by way of infertility) and is using it to breed his own army of Krogan. Everybody (except Wrex) figures you should blow the whole facility to hell to destroy it.
What I don't get is why they feel the need to destroy the cure as well. They could've taken it and used it to save Wrex's whole species. I can understand blowing up the facility to destroy the Krogan army, but was it really necessary to doom a entire race to extinction (practically)?
When I played through it, I was really expecting there to be a choice to take the cure and save the Krogan, but nope. I think that this probably would've been a good area for a Paragon/Renegade choice (I mean, you can choose to let another species live or die later that is even worse than the Krogan....).
(Random Note: A Council species used biological warfare? Not very diplomatic.....)