It can mostly be ignored, but uFAI affects physically-nearby aliens who might have developed a half-Friendly AI otherwise. (But if they could have, then they have counterfactual leverage in trading with your uFAI.) No reason to suspect that those aliens had a much better shot than we did at creating FAI, though. Creating uFAI might also benefit the aliens for other reasons... that I won't go into, so instead I will just say that it is easy to miss important factors when thinking about these things. Anyway, if the nanobots are swarming the Earth, then launching uFAI does indeed seem very reasonable for many reasons.