Controversial material is difficult to address in any epistemic system, and is frequently poorly covered.

If you subscribe to criticisms of establishment ideology, and some of those have merit, there is a pervasive bias against numerous valid, credible, or meritorious viewpoints, contributions, contributors, and voices.

(There is also a great deal of quite valid rejection of flat-out bullshit.)

One can easily find numerous instances of this. An example from my present reading, H.A. Guerber's 1906 anthology The Myths of Ancient Greece and Rome, specifically notes in the preface, "great care being taken, however, to avoid the more repulsive features of heathen mythology".

Earlier enyclopedias either explicitly followed institutional gospel, or faced censure and criticism for failing to do so.

Another instance of which I'm aware, having run aacross it myself, comes from the 1874 Chamber's Encyclopedia, a British work with an authorised American edition ... to which some changes were made. The British publishers took umbrage:

In the interests of literature, and in defence of their rights as authors, Messrs Chambers have to make the following Satement regarding an American edition of their Encyclopaedia:

By an arrangement with Messrs Lippencott of Philadelphia, they were furnished with duplicate stereotype plates of the work, in order that it might be simultaneously printed and issued in the United States. After a time, the American publishers began to make extensive alterations to the articles, a thing which had not been contemplated in the agreement. Had the alterations been confined to bringing the information up to a more recent date, or correcting errors of fact, nothing need have been said about it. But it is a serious matter when, in a re-issue of a work, statements and opinions are introduced which are repudiated and hateful to the original proprietors, their name all the while appearing on the title-page. That Messrs Chambers have reason to complain of being placed in this unpleasant and false position by the American edition of their Encyclopaedia, will admittedly by any one who will look at the following alterations, selected from a number that could be noted....

Among the contested entries, free trade:

Free Trade (Original Edition). 'This term, when used so late as twenty years ago, expressed a diputed proposition, and was the badge of a political party; it now expresses the most important and fundamental truth in political economy. From its simplicity, it affords, to those who expect to make political economy an exact science, the hope that they have obtained an axiom. But it has in reality been established as the result of a double experience --- the one being the failure of all deviations from it, the other being the practical success of the principle during the short period in which it has been permitted to regulated the commerce of the country.'

And how might one possibly offend? Oh...

Free Trade (American Edition), 'a dogma of modern growth, industriously taught by British manufacturers and their commercial agents. For many years certain political economists have laboured to establish this theory upon a reliable basis, and have asserted that the doctrine represents an important truth; but no nation has attained substantial prosperity except by protection to native industry, whether avowed or disavowed. The doctrine had no foothold in the policy of any nation, and had no legislative birth until put forth by Sir R. Peel in 1846....

Also Protection, Slavery, and:

[A] slanderous imputation concerning His Royal Highness the Prince of Wales, which we should be ashamed to copy.

https://archive.org/stream/chambersencyclo00unkngoog#page/n1...

https://old.reddit.com/r/dredmorbius/comments/4xe2k1/chamber...