I was not aware of Catholics being persecuted by the Nazis due to their religion, but I never did stay awake in History class at school.
I do remember that Jews, Homosexuals, Gypsies and people with mental illnesses were deported to concentration camps, tortured and killed. Whether Jewish, Homosexual, Gypsy or a person with a mental illness (or a Catholic for that matter), the pain and suffering is borne by individuals and therefore their suffering is the same.