In this setting there is no difference in value between the life of an evil person and the life of a good person. Killing Shinji Matou for gleefully risking lives is no different than killing Sakura Matou for innocently and accidentally risking lives.
And again, I'll reiterate: when all parties are equally informed as to what they're risking--meaning their lives--then arguments about the worth of what they're risking death for is pointless. Fiore putting her life on the line in a kill or be killed situation for the sake of her legs is just as valid as somebody who risks their life for the sake of saving a thousand innocent lives. The risk is the same for both. In the closed circuit of the ethical situation they have formed, what they all want is equally valid as well. You could say that Kairi is equal parts scumbag for his willingness to kill a disabled woman who just wants to walk again as you could say that Fiore is a scumbag for her willingness to kill a guy doing his job and earning his keep.