I don't think Madara is lying. The Kyuubi incident is questionable, but I believe that it was a natural disaster. I doubt Madara, who I believe to be a mastermind, would simply trust that the Kyuubi could destroy Konoha. Plus I doubt that he would risk losing his secret weapon so easily if he did in fact have control over the Kyuubi.
Madara is my hero btw.