Well, you said "Luther was nuts. That’s common knowledge." But which depends upon if he supported Roman nuttiness.
However let us heard the words of the great Catholic historian Joseph Lortz on a certain Doctor of Theology (though he concluded he also was a heretic as per Rome):
"The problems of an adequate treatment of Luther are obvious from several points of view. First, Luther is an intellectual giant, or, to use a word from Paul Althaus, an "ocean. " The danger of drowning in him, of not being able to come to grips with him satisfactorily, arises from his tremendous output, but no less from his own original style... It sounds banal, but cannot be left unsaid: Luther belongs in the first rank of men with extraordinary intellectual creativity. He is in the full sense a genius, a man of massive power in things religious and a giant as well in theological interpretation. Because of this, he has in many respects shaped the history of the world--even of our world today." (Catholic scholars dialogue with Luther, Jared Wicks Loyola University Press, 1970; http://beggarsallreformation.blogspot.com/2006/04/defending-ohares-facts-about-luther_29.html)
Luther was a devout Catholic priest, at one time (before he went “nuts”).