"BTW, we Catholics can cite Early Church Fathers discussing The Catholic Church."
But not The Roman Catholic Church. That did not come until later. Ignatius began to use the term for the universal church around 107 A.D.. It did not apply to Rome as he was writing to the church at Smyrna. You guys are making me into a history buff and I'm getting off my sola scriptura game.
"That is oral tradition I just made-up"
But it's as good and as valuable as some of the other stuff I've seen on this thread.
The gnostics, and heretics were hardly part of the church however (and that's where protestants get a lot of their crazy ideas).
Further you will note that none of the 5 ancient sees looked anything like the Baptists. (Fr proof check out the reccently discovered church in Jerusalem).
Others call us "Roman" or "bastards"
"Roman" as a modifier for Catholic really came into vogue when the inhabitants of Perfidious Albion, the Anglicans, tried to pretend they were Anglican Catholic and were part of the same Universal Church as Roman Catholics
Thus in the "Catechetical Discourses" of St. Cyril of Jerusalem (c. 347) he insists on the one hand (sect. 26): "And if ever thou art sojourning in any city, inquire not simply where the Lord's house is--for the sects of the profane also attempt to call their own dens, houses of the Lord--nor merely where the church is, but where is the Catholic Church. For this is the peculiar name of the holy body the mother of us all."