Used to be an insult towards Catholics, may offend if used today. Calling someone a papist in the wrong context can be very disrespectful.
Pro Tip 2/3
Historical Context
More common during times like the Protestant Reformation; rarely used now. In historical novels set in the 16th century, the term papist occurs more frequently.
Pro Tip 3/3
Cultural Sensitivity
Be aware of religious sensitivities; 'papist' might be interpreted as showing bias. Use a neutral term instead of papist to avoid misunderstanding or offending someone.