How do you convince a JW that every decision that comes from the Governing Body is not from God?
Get them to acknowledge that Jehovah IS infallible and then quote them from the FDS itself;
Watchtower of March 1, 1979 page 23, “The ‘faithful and discreet slave’ has alerted all of God’s people to the sign of the times indicating the nearness of God’s Kingdom rule. In this regard, however, it must be observed that this ‘faithful and discreet slave’ was never inspired, never perfect.”
or
Jehovah’s Witnesses – Proclaimers of God’s Kingdom, 1993, page 626, “Jehovah’s Witnesses … recognize the Watchtower magazine and kindred publications to be the ones used by the faithful and discreet slave to dispense spiritual food. They do not claim that this slave class is infallible…”