I think we have to take this as motivation for war with the aliens, rather than giving into or ignoring their demands. Assume that the torturers try this sort of thing with more than one set of victims. If any of the victims successfully defeats the torturers, that spares the would-be subsequent victims from the dilemma. Assume that there are multiple species of aliens that would try this torture technique, and some will concoct more persuasive versions of their threat. If none are stopped, we receive a series of alien torture threats that continues until we run into one with a threat so horrible we decide to kill ourselves. So we need to stop them, to the best of our ability, because we need other threatened aliens to try to stop the torturers they encounter, so the torturers who would successfully threaten us into extinction get killed off before they encounter us.