Tehran, April 18 -- In a dim, windowless cell inside a detention facility in Iran's southeastern city of Kerman, 29-year-old Borna Naimi clings to fragments of normalcy--his young daughter's drawings taped to a wall, small reminders of a life interrupted.

A karate athlete, a father, and a member of Iran's Baha'i community, Naimi has become the latest emblem of what rights groups describe as a deepening and systematic campaign of persecution by Iranian authorities against the country's largest non-Muslim religious minority.

Arrested on March 1 by masked officers linked to Iran's Islamic Revolutionary Guard Corps (IRGC), Naimi's detention quickly descended into a pattern of abuse that mirrors longstanding allegations against the Islamic R...