Tested with greekfantasy-16.4.17.jar / Forge 36.1.16
Tested in single and multiplayer world (dedicated server)

As soon as "favor" is disabled in config, Many monsters from Greek Fantasy aren't hostile/attacking anymore without being attacked first. This includes Cyclopes, Harpies, Furies, Mad Cows and Cyprians. Haven't tested all monsters yet to be honest.

Strangely, this has an effect on vanilla Zombies, too. They aren't attacking/following anymore.

Even after re-enabling favor in the config, the AI stays broken for that world. Creating a new world seems to fix the AI and making all monsters behave normal again.

When joining a world, these errors appear, which may be connected to favor, if I am not mistaken:

[20:46:56] [Netty Server IO #1/ERROR] [minecraft/ArgumentTypes]: Could not serialize greekfantasy.deity.DeityArgument@7a9fa1c7 (class greekfantasy.deity.DeityArgument) - will not be sent to client!
[20:46:56] [Netty Server IO #1/ERROR] [minecraft/ArgumentTypes]: Could not serialize greekfantasy.deity.DeityArgument@6f615ca8 (class greekfantasy.deity.DeityArgument) - will not be sent to client!
[20:46:56] [Netty Server IO #1/ERROR] [minecraft/ArgumentTypes]: Could not serialize greekfantasy.deity.DeityArgument@482fa2dd (class greekfantasy.deity.DeityArgument) - will not be sent to client!
[20:46:56] [Netty Server IO #1/ERROR] [minecraft/ArgumentTypes]: Could not serialize greekfantasy.deity.DeityArgument@83b75e9 (class greekfantasy.deity.DeityArgument) - will not be sent to client!

The Netty errors are not related. Those are leftover from server-client command syncs.
I didn't do much testing after adding the global "favor disable" config, but I found the line of code I was missing. This should be fixed in the next release (which will probably be this month).
Thanks for reporting!