I think their reluctance to take on the whole camp is supposed to be pragmatic, not conscientious.
Druids aren't supposed to be 'good', nor do they like big moves in the ecosystem, so wanting to exterminate the gobbos or not doesn't say much. And the Trial of Thorns is a result of the Shadow Druids foreseeing an invasion from the Absolutes forces
If there's an evil race in the Monster Manual, there is a 75% chance there's a backdoor blurb there just to legitimize someone's monster pc at the table. You get inured to it after a while.
