Hi, we are being asked why the argument is flawed. While there are a few ways to attack this argument (not sure that hiding is the same as obstructing police, assuming that arrest for a crime they did not commit is doing harm), I simply do not know that this moral duty guarantees that one would be morally right to hide ones child.
A is not what the argument does- this is a narrow example to prove a narrow point.
B actually does describe a weakness. Perhaps there are other moral duties that override that to prevent harm to families, such as to aid law enforcement.
C is not what happens, in fact, there argument assumes that preventing police from an arrest obstructs justice.
D is not really relevant
E is also not relevant, the actual innocence is not in question