Please note that this is a question and I am not trying to insult anyone.
The term "Papist" is often used as an insult in anti-Catholic rhetoric, and I have not heard it used by Catholics to describe themselves (except in an ironic or humorous way).
I'm wondering why the term is considered derogatory. Etymologically, it would simply means someone who believes in the institution of the Papacy, which is not only accurate for Catholics but something they are definitely not ashamed of.
The reason I'm wondering this is because it's somewhat of a shame that there's no neutral term for the RCC. By calling them the "Catholic Church" one implicitly accepts their claim to be the church that is catholic, which is an ecclesiological claim no-one outside the group would agree with. Sometimes Protestants call them the "Roman Church" or "Roman Catholic" in order to avoid this difficulty, and I have also heard of these terms used by Catholics to distinguish themselves from Anglo-Catholics. But this is also considered derogatory by some Catholics. Also it is not wholly accurate unless it is meant to be "the churches in communion with the Roman Church" since this term is meant to include Eastern Rite Catholics, which are not "Roman" except in the sense that they are at the top level part of the same organization.
Anyway, I'm wondering about the origins of the term "Papist" and why it is considered derogatory by Catholics. I am mainly asking why it is received as derogatory by Catholics, who obviously don't take offense at being described as those who believe in the Papacy since they don't think this is a bad thing.