I would replace the word “morality” with “ethics” here. (see also)
As to figuring out whether or not it should be legal for a parent to kill their child, yes it is important for libertarians to understand they don’t have rights, because other people will ask about it.
You do realize that there doesn’t seem to be a single “libertarian” (stranger doesn’t call himself this AFAIK) in agreement with you right? Even if there is, it is a vast minority. This says nothing about the public at large, who also doesn’t seem to share your views.
I really don’t see why you are still posting when there are questions about your theory on the first couple pages which you can’t seem to answer. Even if someone thinks that your theory doesn’t fall flat on its face, it certainly doesn’t go very far.