It's funny when Protestants think Catholics as not proper Christians. The Bible says Jesus appointed Peter pope, and that lineage continues today, despite the utterly corrupt popes between then and now. Whereas Martin Luther, the first Protestant, came up with Lutheranism. He did not get any kind of direct endorsement from Jesus or God. He simply said "this is what I believe." And the rest of Protestantism followed from there. So since all the Protestants broke away from Catholics, it stands to reason Catholics are the only "true" Christians in any kind of genealogical or historical sense. The Protestants are renegades, unauthorized by Jesus.