The Power and the Glory Sin Quotes

How we cite our quotes: (Part.Chapter.Paragraph.)

Quote #10

"Pride was what made the angels fall. Pride's the worst thing of all. I thought I was a fine fellow to have stayed when the others had gone. And then I thought I was so grand I could make my own rules." (3.3.72)

They don't call pride the root of all sins for nothing. But here's a question: if pride is the worst of sins, then why does the priest name it as one of the venial, lesser sins? So many questions, such few answers.