Life-extension provides more time. Freedom is time. To do what I want to, I need space in which to do it. Imprisonment is being confined to a small space. Imagine a future time with human colonies in space, on the Moon, and on other planets - and considerable space travel between them.
Freedom is space.
According to the best evidence available to me, if I die I lose all freedom - all my options have expired. Death is the biggest and ultimate enemy of freedom. My highest priority as a freedom-lover is to overcome death and render it obsolete. Death must be killed. Freedom is physical immortality.