I agree with this chain of reasoning. The fact that books were burned in other times and places does not imply that this particular book-burning happened. Especially when the other book-burnings left a large "paper trail", and the claimed book-burning left none.
If I may mention more of my own thoughts about the general idea of the burning of books:
The claim that books were burnt by Christians does not necessarily imply that a powerful orthodox system of belief was enforced by "shepherds" using strong-arm tactics against their sheep.
An example that comes to mind is from the book of the Acts in the New Testament.
[Scene: Paul has been preaching the gospel in Ephesus during a 2-year period of time. Many miracles/supernatural events are attested to, and a large number were converted.] (Acts 19:1-17)
"...many that believed came, and confessed, and showed their deeds. Many of them also which used curious arts brought their books together, and burned them before all..." (Acts 19:18-9, KJV)
The chain of events which leads up to this burning is a bit strange, but it includes none of the usual suspects for a book-burning.
--No agents of civil government implicated
--No repressive laws mentioned
--No reference to a command by a religious leader that books must be burned as proof of piety
--No punishments recorded against holders of said books
--No commandment recorded that any books were to be forever placed on a list of "forbidden books"
This scene did include a few surprising positive notes:
--An apparent decision by a large number of people that belief in Christ precluded placing any trust in these "curious arts", often referred to as "magic" by later translators.
--An implicit approval by Apostolic authority (Paul)
--A reluctance by Paul to make the burning of specific books a necessary component of membership in the church.
Perhaps I am spending too much time with this one particular case of book-burning. Yet I think this points out that books being tossed into a fire does not necessarily imply an oppresive authority attemting to purge certain common beliefs. The believers may be able to make the decision themselves!
For every claim of book-burning, we do need to ask if it actually happened. (Thanks for keeping that question in the forefront of your statements.)
If we find that it did happen, I think we need to ask how it happened. Not all cases are as easy to dissect as the one I mentioned. But I doubt that every case of book-burning in history falls into the category of oppresion.