Your comments

I observed such behavior among bots.

If you have trouble replicating this here's the easy way :

Pick Small Map. Don't build Tavern & Slaugherpen. Soon your intelligent creatures will rebel and you will see how it all goes. Same may happen to bots, except AI doesn't bother dealing with this problem which will end up with all units rebelling.

Just so you know, rebelling units have the same color of shield as normal ones, thus are considered as allied/loyal by others. For such reason, units that are not rebelling can't fight back and end up being angry since they are constantly disturbed.