Logic 101

Mechanic: "The Collectors? They're real? They took everyone! This is all the Alliance's fault!"
Shepard: "What?"
Mechanic: "No one bothered us until the Alliance put in those defense towers!"
Shepard: "Correlation doesn't imply causation."
Mechanic: "Huh?"
Shepard: "Post hoc ergo prompter hoc is one of the oldest logical fallacies in the book. Just because A happened, then B occured, does not mean that A caused B."
Mechanic: "But..."
Shepard: "No other colonies that were attacked had any new Alliance defense towers."
Mechanic: "But that Chief Williams showed up, then we were attacked! She was on Eden Prime, and they got attacked, too!"
Shepard: "Well now you've at least got two instances, which is a stronger argument. But look at the other common factors. Each human colony attacked, including Eden Prime, Horizon, and Freedom's Progress, were outside of Citadel Space. The ones attacked most recently are outside Alliance space. Isn't it more likely that building a colony outside of the borders of a government which might be able to protect you could lead to an opportunistic foe attacking you?"
Mechanic: "It's the Alliance's fault!"
Shepard: "... OK, sure, whatever. Look, we can use the guns."
Mechanic: "They need to be calibrated. They've never worked before!"
Shepard: "Thus, they'll never work? Seriously, do you even hear yourself? Have you ever been attacked by Collectors before? No? So, that means they should never attack you, right? Wrong! Just because something has never occurred, does not mean that it will never occur."
Mechanic: "It's still the Alliance's fault."
Shepard: "But... *sigh* Shut your pie hole, open the door, and stay out of my way. Dumbass."