An interesting thing I'd like to note about that article is that it doesn't state how many times civilians tried, and failed, to prevent a mass shooting (most likely because this data is much harder to find), and that at least half (I didn't count) of the ones stopped by civilians was through a tackle, rather than a gun. I will however give you that that article does show some rather nasty truths, and you probably have a point.
Golden: When someone brings a gun it is probably going to end badly for me regardless of if any civilians have one or not. I will certainly agree that if anyone is close enough trying to take down the shooter with any means may be the best scenario, but distance is important.
The trick is that if the government goes totalitarian on us they aren't going to care about civilian casualties. As Big Lutz brought up, insurgencies are a problem if you don't want to kill civilians. One of the defining things about a fully totalitarian government is they wouldn't care. Carpet bomb an entire city? Why not, it will be an excellent example to the others exactly how resistance is treated. The way to break someone isn't to kill them. It is to make it clear that if they try anything everyone they care for is going to die. Of course that does have a chance to backfire, but how often do governments think of that, compared to how often they disregard civilian lives?
Idsman: I wouldn't argue that, it makes sense in terms of on the shooting range, but my point is a real situation like this is not like the shooting range, people can have very different reactions to stress. Some probably will still be a very good shot. I worry about the ones who pull out a gun while panicking (yes, you may be trained not to do this, but if you are panicing how much of your training do you really remember, or care about?) The problem is it is impossible to know until it is already too late.
