To the guy that said the documentary DOES NOT say Constantine started Catholicism, I'm going to quote it:
"Constantine the Great goes down in history as being the emperor who sets up this Roman Catholic Church." ~19m:35s
"The Roman Catholic Church began its official existence in 313 A.D. with Constantine calling a council of Christian leaders in his realm . . . He formed that official church structure that would later become the Roman Catholic Church." starts at ~19m:56s
"Constantine had pulled together and sanctioned a meeting of churches and as a result of that Catholicism was invented." ~ 20m:46s
"The Catholic Church formed based on Constantine." ~20m:59s.
"What you have to understand about Catholicism is that without Constantine there is no Catholicism." - ~21m:20s