After years of searching I have finally found the definitive case of Christians burning books. I don't mean Christians rooting out heretical works or pagan propaganda but the actual indiscriminate destruction of books because they are, well, dangerous. The culprit appears to have been one Richard Cox, Dean of Christ Church, Oxford and later Bishop of Ely. Not a very famous man today but he once had a reputation as a leading puritan and militant during the reign of Edward VI (1547 - 53) although he seems to have quietened down a bit under Elizabeth I after she gave him a bishopric.
Anyway, the story goes that he utterly destroyed the entire University Library at Oxford during 1549 when he was appointed by the king to 'visit' it and ensure Protestantism was being observed. The case against him is that he was indeed a visitor, that the medieval university library ceased to exist about that time and he is blamed by writers a century later. Even if Cox was innocent, it does seem that radical Protestants did do a lot of damage to Oxford libraries as most of the books and manuscripts reported to the visitors of the Catholic Mary I (reigned 1558 - 58) are still in situ to this day.
I'll write something up on this as it is also relevant to my PhD.