For my defense of Catholicism, I must first note that SOGFPP has already written a good deal, and written it well here:
http://www.religiousforums.com/forum/showthread.php?t=6126
I have on top of all this already proven in this thread that peculiar Catholic doctrines have already existed. For example, the term "Catholic" referred to the "Catholic Church" goes back to well before the year 107 by way of Ignatius (the Christians who called themselves "Catholic" never meant "catholic" with a little "c" until people wanted to start justifying schisms), or as another, that first century Christians did fast on Fridays. These are common points of dispute.
I have also demonstrated that while the Apostles taught unity, they didn't accept every schism that came along. Telling someone that they should castrate themselves is not kosher for that purposes. Calling others "antichrists" also seems quite "sectarian" by today's non-denom standards.
Rather than focus on all the details, I can answer a specific challenge if it comes. I focus instead on the bishop and the Eucharist. The term "bishop" is found in the Bible. Since it is the same word as "episkopos," then it is also an exact equivalent.
Christ established the bishoprick. That is the only office that He established. The Apostles started the deaconate, and we don't know when or where in the first century the episcopate separated from the presbytery. We do know that it was widespread by the year 107, so it happened at least in John's own lifetime, maybe while others were alive. If they didn't have a problem with it, then neither do I.
When Christ established His Church, He did not establish some amorphous entity nobody could identify and which taught every possible belief, but we accepted everyone in the name of "unity." That contradicts the multiplicity of anathemas, curses, and attacks in the New Testament and the Fathers against people who taught differently than the Apostles.
Paul gives quite a bit of information concerning the role of the bishop. What he doesn't do is explain where it comes from. Where was it instituted, and why? Exactly what role does it play? He doesn't quite say. He does go into great length about what he does. What you can gather is that he "rules" the flock of God.
What, then, do we know abou it? Quite a bit, actually. I mentioned before Clement of Rome, and that he was a companion of Paul and wrote a letter in the year 70 AD. Here is what he says:
"Our apostles likewise knew, through our Lord Jesus Christ, that there would be strife over the bishop's office. For this reason, therefore, having recieved complete foreknowledge, they appointed the officials mentioned earlier and afterwards they gave the offices a permanent character; that is, if they should die, other approved men should succeed to their ministry. Those, therefore, who were appointed by them or, later on, by other reputable men with the consent of the whole church, and who have ministered to the flock of Christ blamelessly, humbly, peaceably, and unselfishly, and for a long time have been well spoken of by all--these men we consider to be unjustly removed from their ministry. For it will be no small sin for us, if we depose from the bishop's office those who have offered the gifts blamelessly and in holiness." (I Clement 44.1-4)
Here, Clement is rebuking the Corinthian church. Paul has died, and the fight that he had to deal with has resurfaced again. They have deposed the bishop to put their own man in. Clement is, thus, telling them here how the bishoprick came about. Christ founded it, and taught that when a bishop dies, his position is supposed to be filled immediately.
The Scripture doesn't explain the origins of the office of Bishop, but we know from here where it came from. It is also in harmony with the Gospel of John's claim that all the world's libraries couldn't possibly hold all that Jesus did. Today, this doctrine Clement is attributing to Christ is called Apostolic Succession, and it is a linchpin of Catholicism. One can only claim to live in harmony with this teaching of Jesus by participating in a church that has such succession.
Another Church Father, this one in the mid-second century, in his struggle against Gnostics:
"But again, when we refer them to that tradition which originates from the apostles, and which is preserved by means of successions of presbyters in the Churches, they object to tradition, saying that they themselves are wiser not merely than the presbyters, but even than the apostles, because they have discovered the unadulterated truth...[a long explanation of Gnostic thought]...It is within the power of all, therefore, in every Church, who may wish to see the truth, to contemplate clearly the tradition of the apostles manifested throughout the whole world; and we are in a position to reckon up those were by the apostles instituted bishops in the Churches, and to demonstrate the succession of these men to our own times; those who neither taught nor knew of anything like what these heretics rave about. For if the apostles had known hidden mysteries, which they were in the habit of imparting to `the perfect' apart and privily the rest, they would have delivered to those whom they were also committing the Churches themselves" (Irenaeus, Against Heresies, Book III, chps. II-II).
Irenaeus, also, is not far from the Apostles, though unlike Clement or Ignatius, he did not know them. What he emphasises is the same thing Clement emphasised in 70: that there was a succession from the Apostles, and that these bishops were authoritative. He is, here, using it to confound the Gnostics. In essence, he is saying that these men teach the same thing everywhere, so if the Gnostics were right, why would this be so? This question is equally poignant now, because the Church that Irenaeus is talking about is indisputably Catholic. If there was a falling away, we wouldn't expect this kind of unity, much less one that could appeal to history.
A very forceful statement comes from Ignatius. He said:
"Flee from divisions, as the beginnings of evils. You must all follow the bishop, as Jesus Christ followed the Father, and follow the presbytery as you would the apostles; rspect the deacons as the commandment of God. Let no one do anything that has to do with the church without the bishop. Only that Eucharist which is under the authority of the bishop (or whomever he himself designates) is to be considered valid. Wherever the bishop appears, there let the congregation be; just as whereever Jesus Christ is, there is the Catholic Church. It is not permissible either to baptize or to hold a love feast without the bishop. But whatever he approves is also pleasing to God, in order that everything you do may be trustworthy and valid" (Ignatius to the Smyrnians 9).
This man I have mentioned before, is the disciple of John. He wrote it in simple matter-of-fact instructions, just as we'd read in Paul. He simply assumed this to be true, and he did this from Ephesus all the way to Rome.
I will close with proof on how they worshipped.
