Well, i would argue that the host system takes priority until a system under construction is viable on its own.
Generally thats true, afterall its why its ok to remove a tumor (even if that tumor may have a brain which can happen).
the difference here is we have a host system who forced the subsystem into existance and waited long enough for the subsystem to develop that it potentially could suffer or expiernce its death. So the analogy breaks down quickly.
If I abduct a human, force them to be biologically dependant upon me against their will, then murder them I dont kind it an acceptable excuse that just because they were dependent on me (as a consequence of my actions) that I had a right to kill them.