Joseph F. Merrill teaches that, while the President of the Church is not infallible, when he speaks authoritatively, no one should reject his teachings.
Joseph F. Merrill, Conference Report (April 1941), 51
Do the people of the Church want a safe guide to what is well for them to do? It is this: Keep in harmony with the Presidency of this Church. Accept and follow the teachings and advice of the President. At every Conference we raise our hands to sustain the President as prophet, seer and revelator. Is it consistent to do this and then go contrary to his advice? Is anyone so simple as to believe he is serving the Lord when he opposes the President? Of course, the President is not infallible. He makes no claims to infallibility. But when in his official capacity he teaches and advises the members of the Church relative to their duties, let no man who wants to please the Lord say aught against the counsels of the President.