I made a Drow Lolth priest to check out the evil path, but when I got to the druid battle and took the side of the goblins... The goblins just attacked me and the druids didn't retailiate. I even shot one of their prone warriors. How much more evil can you get ? But the goblins didn't take the hint. So, they didn't want to let me fight on their side. Not that I want to be evil, but Larian wants us to try it, so I tried, but there seems to be a glitch.
I agree this part is too much oriented towards good. There is nothing much you can do apart from either take the side of the grove or look from afar and eventually clean the remaining goblins.