If you have a large empire, chances are there was large scale conquest involved. Likely all "civilizations" involved small scale conquest of tribes.
So the academics are all in arms about Diamond writing a pretty engaging nonfiction book that accessibly integrated a half-dozen historical / political theories into an interesting integrated theory. Was it perfect? Hell no, no way it was. Is there roots of truth in it? There has to be. More than anything, reading the book was thought provoking, because all history taught in schools is basically a bunch of personalities/leaders and battles, and almost no investigation of other factors outside of the human events.
What's also bizarre is reading various modern historical analyses of the Mongol invasions as "eh, they weren't that bad". Like... what?
I'm fully willing to admit European empire building was flagrantly unacceptable from the lens of the modern conception of universal human rights. But that Euros were some especially brutal oppressors/conquerors compared to the whole of human history? Come on. I mean... the Mongols. AND they almost conquered Europe.