The Flying Knife Mantis, with speeds up to several times the speed of sound, made it essentially a death sentence in front of infantry. Apart from structurally hard armor and energy shields, there basically wasn't much else that could defend well against such a murderous weapon. Automated and highly intelligent defense weapons would be helpful, but even Star Alliance troops didn't have this kind of close-range, intensive defense weaponry equipped at the mobile infantry level, let alone these poor, solo explorers.
Bai Zhongqi didn't take lives indiscriminately, though he wasn't sure whether the capricious girl Lan Xue was telling the truth. Yet, he could discern that these people harbored ill intentions. They exuded a malice that made Bai Zhongqi think they had probably done their fair share of wrongdoing, so he took out the ones he disliked most with a wave of his hand.