Sinclair's quote at the end bothers me. Humanity already has colonies at least out to Proxima and Orion and where ever Arisia is, so even if the sun goes nova, then (some aspects of) our culture will survive. (Maybe they are marginal colonies and highly dependent on Earth still?)

If he had argued that the station is important because it'll help stop wars (see: Earth-Minbari) that might take us out root and branch, that makes a bit more sense than worrying about the sun going nova. It's an argument for our interacting with other races and making peace, rather than just going out into space.

Of course, we're about to hit a Big-Ass war that might take everybody out root and branch, so maybe it's foreshadowing...