When does it become okay to kill for your freedom?
At the same point at which it becomes ok for any other reason as well.
I agree.
As for the general topic of killing itself, my opinion is that it's always contextual. I don't believe there's a blanket example you can use and from then-on apply it to say that killing is either okay or not okay in any circumstance.
I think for the most part, people do
not have to die. Everyone, no matter who you are, has a family, friends, people who care about them. When you kill a man, you affect at the very least, two other people, whose state affects the people around them. This ripple effect is almost as bad as the death itself, if not even worse in some cases.
Also, Goober, whilst my personal belief is that it would be permissible by my view to shoot the chainsaw wielding bloke and inflict lethal force, I don't believe that it's the only option. What if he's at a distance from you, could you not attempt to get him talking? If you could get him to calm down and drop the thing without anyone being wounded or killed, that, in my opinion, would be the most positive conclusion to the series of events possible from the point at which you became involved.
And on topic, I agree with NGTM-1R's response. It's definitely not the first option to be taken, but if there's no other way, having your freedom taken isn't okay either. And it is a rather significant issue. Especially if other people are affected and their freedoms are also taken, I think one would be in the wrong to not do anything.