one of the things that i haven't read yet on this thread is the outcome if the males out number the females. that is, the long term outcome.
i remember reading an article about women in rural china, where the situation of one child policy and the desire for males has been going on long enough for there to be more available adult males than available adult females. common practice: steal/kidnap females from their families (or husbands and children), and then force them into new marriages with their kidnappers--a process usually accomplished by a fair bit of violence against those women (beatings, rape, sold to families who want wives for their sons, etc).
i agree that an unwanted child being raised by those 'caregivers' is probably not going to lead to positive outcomes for those children (eg, potentially subject to emotional or physical abuse, neglect, and obviously the violence of infanticide), but the long term consequences of killing female children more often than not also leads to a long term situation of violence against women as they become a resource for reproduction, one that can be stolen, bought or sold, etc.