Do barbarians really make no difference between the AI and human player units?
Yesterday I was trying to lure an Aztec settler into a nearby barb outpost (we had an active friendship declaration, so I couldn't just strait take the settler). The spearman left the outpost, but only to chase my unit exclusively. That's even when I was hiding my unit behind the settler, and the spearman was on the next tile to the settler. The barb would still move towards my unit ignoring the AI on the next tile
So in the end (after 10 or so turns of such dancing) the settler departed in the opposite direction from the camp (and my cities, so at least something) and founded a city there, and of course I unleashed my rage onto the camp, sparing no one 
And I've had numerous other cases when barbarians prefer my units or cities to the AI even when AI is nearer and visible (if that applies to barbs).
Yesterday I was trying to lure an Aztec settler into a nearby barb outpost (we had an active friendship declaration, so I couldn't just strait take the settler). The spearman left the outpost, but only to chase my unit exclusively. That's even when I was hiding my unit behind the settler, and the spearman was on the next tile to the settler. The barb would still move towards my unit ignoring the AI on the next tile


And I've had numerous other cases when barbarians prefer my units or cities to the AI even when AI is nearer and visible (if that applies to barbs).