Before meeting Juliet Stameros, Calabast tried her best to shape his views on the Penitent Sisters.
According to her, the Penitent Sisters were victims and deluded sheep. The true masterminds responsible for committing all of the atrocities were the evil cult leaders who originally devised the doctrine that the phase of damnation represented boys!
Those at the bottom only did as they were told and learned everything the cult passed on. The insular, restrictive upbringing of the Penitent Sisters prevented them from learning any alternative interpretations. Critical thinking was something completely alien to these devoted worshippers!
Ves was well aware of what Calabast tried to do. He didn't buy into her story. Not completely.