Alternately, defining harassment solely based on the perceptions of the receiver, as many organizations do, creates a comparable problem of subjectivity. Perhaps something like commonly-agreed "community standards" should be the guide.
Perhaps the 4 month old is not "manipulative" per se, but it also cannot be argued that the kid is doing much of a cost-benefit analysis as to whether it's worth waking Mom and Dad up for this (whim/legitimate need).
I will be downvoted for this, but the whole focus on marginalized people at the cost of everyone else, and not allowing any reverse-ism debates pretty much sums up the site.