Father Lou was a true Priest with a genuine calling. What he did for the homeless alone in the South Bronx through SEBCO is amazing. Believing in your family may make you naive, but it doesn't make you a bad person. Vince having a master plan that included Lou becoming a Priest is something out of a terrible straight to DVD mob movie.
A true priest? I don't think it was any kind of master plan but I'm under no illusion that Father Lou didn't know exactly who his brother was. Furthermore, he played along and lied about the crazy act when he knew it was all a charade.
