He was raised to BE a Catholic, that does not make him a Catholic. A lot of people are raised in Catholic homes, go to church and mass with the family but are never truly Catholic, per se. They put it on forms and such when asked but have never studied the faith and what it IS to be a Catholic. I found this out as a life long Catholic only after I enrolled in a religious education/RCIA program at my church. There is more to it that the name, believe me.
Maher’s bio says he quit the church in his teens. I assume that he was baptized and confirmed as a Catholic.