I'm not saying I agree with the philosophy, just that that's how the antagonists in the book thought: we're scared, we don't trust anyone, so snuff out any oth

I'm not saying I agree with the philosophy, just that that's how the antagonists in the book thought: we're scared, we don't trust anyone, so snuff out any other possible competing space-faring species in the cradle. Of course, it's entirely possible that it simply isn't practical to traverse interstellar distances at all, other than sending dormant robots on "the slow boat" to explore and "phone home" about what they found. More likely there are better ways to travel, but it might take more than 50 years on manned space travel to discover / devise them.