The phrase "Roman Catholic" is used in accordance with keeping the guidelines against making personal attacks. The RM has posted examples of what is or is not making something personal. You may want to acquaint yourself with them.
From the RM's page:
For something to be "making it personal" it must be speaking to another Freeper, personally.
"Protestants are heretics" is not making it personal. "You are a heretic" is making it personal. "Catholics worship Mary" is not making it personal. "You worship Mary" is making it personal. "Mormons worship many gods" is not making it personal. "You worship many gods" is making it personal.
“Protestants are heretics”
The term “ Roman Catholic” is also used to distinguish between them and the Orthodox, who do not hold to many of the beliefs that the Roman rite adheres to.