I think both statements are true - not all knowledge is recorded by academia, and academia is heavily western biased.

What I suspect is that the down-votes are because the first user was using hyperbole to make a positive comment about our ability to archive these documents and their value. The response points out something that is evident - obviously academic papers do not hold all human knowledge - and shifts the conversation into a not so casual topic of western biases. This sudden shift of the conversation from friendly-casual to geopolitical with little motivation can make some users upset.

OR, as the other person suggested, maybe the mention of 'western bias' is enough to trigger some.