From the datamining thread:
At this rate, the grove’s reaction to the shadow druids should be “hooray, allies!”
Actually, why were they even horrified to learn of shadow druid meddling? Near all of them were completely onboard with this whole ritual. Both groups want the same thing. They clearly have no love for Halsin’s worldview, just join them.
Though, in the game’s defense, one is able to question Halsin giving such a lenient punishment to Kagha (demotion, a pretty heavy one granted, but this could be an unrepentant woman who killed a child). This could hint that Halsin did not master to “stick” side of carrot and stick leadership.