I Love this in the Baptist's reply....
Also, of course, this is written under the assumption that [this Catholic]'s church is the true church and that his concept of the church is the correct one. Needless to say, I reject his concept of the church and reject his assumption that the Roman Catholic Church is the true church.
I have had this happen to me in such discussions. It is a common tactic designed to turn a Scriptural discussion into an "us vs them" (Catholic vs protestant) discussion.
I have taken to calling them on this...If I did not say it, don't assume that I meant it. In other words - stick to what I said and if what I said is firmly based in Scripture, then it remains valid regardless of my own particular faith tradition.
When one does this, and really begins to look at what Scripture calls for in regards to unity, we find that the Holy Spirit desires much more than agreement on five points. Just look at these verses.
20 "I do not pray for these only, but also for those who believe in me through their word, 21 that they may all be one; even as thou, Father, art in me, and I in thee, that they also may be in us, so that the world may believe that thou hast sent me.
5 May the God of endurance and encouragement grant you to live in such harmony with one another, in accord with Christ Jesus, 6 that together you may with one voice glorify the God and Father of our Lord Jesus Christ.
1 Cor 1:10
I appeal to you, brethren, by the name of our Lord Jesus Christ, that all of you agree and that there be no dissensions among you, but that you be united in the same mind and the same judgment.
2 Cor 13:11
Finally, brothers, rejoice. Aim for restoration, comfort one another, agree with one another, live in peace; and the God of love and peace will be with you.
Only let your manner of life be worthy of the gospel of Christ, so that whether I come and see you or am absent, I may hear of you that you are standing firm in one spirit, with one mind striving side by side for the faith of the gospel,
1 Pet 3:8**
Finally, all of you, have unity of mind, sympathy, brotherly love, a tender heart, and a humble mind.
Look at these calls to unity....Jesus wants us to be "One" as He and the Father are One...How much room for varying and conflicting doctrine is there in such a unity?
Peter and Paul are callus to be in agreement, of one mind, one voice etc.
Couple these calls to unity with the instructions in Mt 18:15-18 and the example in Acts 15 where the issue between the Judaizers and the Gentiles came up. They did not agree to disagree...they told it to the Church and they Listened to the Church.
The protestant argument about the visible Church (limited in scope to a local or regional congregation) is blown away by Acts 15.
Even if we allow for differing doctrine in some practical matters, there are deeper differences in Protestantism that touch on matters of Salvation. Lutherans say that the Lord's supper contains the "Real presence" Baptists say it is symbolic. Jesus says unless you Eat my body and drink my blood you have no life in you...But there are different and conflicting understandings of this passage.
Some groups require water Baptism while others deny the efficacy of water Baptism - yet the Bible says repent and be baptized in order to be saved...
These are issues on which all churches should speak with one voice....as they touch upon salvation.
In summary....Call the baptist on the issue of trying to negate the argument by reading into the response something that was not written. Explain that you are not trying to convince them that the catholic Church structure is right. After all, the EO, an equally Ancient Christian Church uses a slightly different (though similar) structure. Tell them that you will stick to Scripture - and then....make them show you - In Scripture - support for their interpretation of "church" (little real authority, limited to local communities etc) and their position that "agree on essentials" is enough. Frankly I've never found a person who was able to meet this challenge.