How far is "near," really? Human civilization took tens of thousands of years just to discover a new continent, and the ocean back then was essentially as vast and impenetrable as space is today. If we ever actually develop near-lightspeed spacecraft, are we seriously assuming the first thing we'd do is build weapons capable of annihilating entire civilizations — and then actually use them? Oh my god, we already have those weapons, and the most likely target has always been ourselves.