Dear Fr. Gregory,
How I sympathise.
Here's another way of putting your point - though I warn you that when I do it it is usually to prolonged silence.
They claim to follow what is in the book, and when asked who canonised the book, tend to say 'God'. Well, let us look at two of the earliest books for a moment.
One of the oldest extant copies of the Scriptures, the fifth century Codex Alexandrinus
includes 1 Clement amongst the rest of the Scriptures as we have them. The other ancient surviving text, the Codex Sinaiticus
includes The Epistle of Barnabas as well as The Shepherd of Hermas.
These are two of the earliest surviving manuscripts of the Scriptures and they have in them books that are not included in the Scriptures we all now use. Who was it decided to leave out 1 Clement, Barnabas and Hermas? If it was God, then why are these books in the earliest manuscripts? Had Sola Scriptura
existed then (and as we know it didn't), then they'd have been telling us these books were there because God put them there. Well, they are there, and there in the earliest complete books.
Fortunately, the Church did not receive a book, it received the orthodox Faith by oral and written tradition, and that Faith enabled it to see that whilst Clement and co, were books that could be read for edification, they were not in the same league as the other books in the two Codices.
I really can't see why a Sola Scriptura
Christian doesn't insist on what is in the earliest books - that would be a consistent line to take. Accept the earliest books, not those edited by the Church.
Mind you, if they did that, they'd have to stop telling us how to interpret the Bible
In this is love, not that we loved God, but that He loved us and sent His Son to be the propitiation for our sins. (1 John 4:10)