Fun fact: Sometimes a lawyer's job is to tell the client things they don't want to hear, to question a client's representations if they appear inconsistent with other evidence, and to refuse to make arguments or take positions that they know to be frivolous.
A telling passage from Zuck's WSJ op-ed: "Imagine everyone has a superintelligent lawyer. Justice would be carried out much more fairly and efficiently than it is today." I'm really not sure this is true!