Why be Catholic?

I recently asked a Catholic philosopher why he's Catholic rather than Protestant. I asked him because he's the smartest Catholic philosopher of his generation, so I was curious to get an answer from the best of the best, instead of the garden-variety Catholic apologist. Here's his reply:

In short: Scripture tells us that the Church is guided by the Holy Spirit (Jn 14:26; 16:13; 1 Tim 3:15). And only the Catholic and Orthodox Churches have a plausible case for having the same teaching as the early Church. Sexual ethics is perhaps the clearest case: Protestants have largely abandoned the teaching on contraception and remarriage after divorce.

He's distilled the Catholic apologetic down to what he considers to be the strongest arguments. It boils down to two arguments, using sexual ethics to illustrate one of the two arguments. So let's to back through his reasons:

In short: Scripture tells us that the Church is guided by the Holy Spirit (Jn 14:26; 16:13; 1 Tim 3:15).

1. I'm not going to rehash 1 Tim 3:15. I've discussed that here:

http://triablogue.blogspot.com/2017/12/catholic-prooftexts.html

2. Regarding the Johannine verses:

i) The promise is made to the Eleven, not to "the Church". 

A Catholic might counter that the promise extends to the successors of the Eleven. If the papacy/Roman episcopate is an extension of the Apostolate, then the promise extends to the papacy/Roman episcope. 

ii) Problem is, there's nothing in these verses, or John's Gospel generally, or 1-3 John, to warrant that extension. 

iii) Moreover, it's not a promise exclusive to Peter and his (alleged) successors. Even if you think the promise extends beyond the Apostolate, there's nothing in the text to limit the extension to a Petrine line, to the elimination of the other disciples to whom the promise was made.

And only the Catholic and Orthodox Churches have a plausible case for having the same teaching as the early Church. Sexual ethics is perhaps the clearest case: Protestants have largely abandoned the teaching on contraception and remarriage after divorce.

1. As I've often remarked, there was false teaching in churches during the apostolic era. There was false teaching in churches planted and overseen by apostles. When the apostles were away, false teaching creeps into their churches. We see that from several NT epistles. So antiquity carries no presumption of orthodoxy or apostolicity. 

2. To my knowledge, early Christian opposition to contraception was inseparable from opposition to abortion because, before modern medical science, it was impossible in principle or practice to separate the two. So that's obsolete. 

3. I think the NT does allow for divorce (for desertion and infidelity). And while traditional Catholics have alternative interpretations, I think those are weaker. But even if we think the passages are ambiguous, the ambiguity cuts both ways. You can't used the ambiguity (assuming it's ambiguous) to rule out the standard Protestant interpretation. 

4. In addition, we need to distinguish between continuity of doctrine and continuity of practice. A practice may be historically continuous but the understanding or rationale for the practice may change over time. For instance, Christians have practiced water baptism since the origin of the Christian faith. As the theology of baptism developed, it came to be viewed as a rite to erase original sin. But to my knowledge there's no evidence that this reflects the original understanding of baptism. Rather, that's a theological innovation. To say something represents "the same teaching as the early Church" is equivocal in that regard.