I don't think there is any conflict between Christ and Gandhi. When Gandhi passed the Vatican said that he was a messenger of Christian Truths. Gandhi was an extreme admirer of Jesus Christ and also of St. Theresa of Avila, a famous Catholic saint.
As far as Christianity being a myth....that has become a kind of popular notion, but even the secular historians really do not believe that. They may think that Christ was not a saint, but they indeed recognize the existence of a Christian sect diverting from Judaism..and at the time it is supposed to have occurred.
here's one site that references a few of the Roman and period sources: