I don't mind such ethical discussions although being called 'evil' just because I don't help the Tieflings is a bit harsh.
Not that you don't help them - but specifically that you don't care about their plight, and that you don't care about what Khaga is doing to the grove or to other innocents. A person may have any number of reasons or motivations for acting as they do - and those are the features that inform the concept of alignment, not specifically the action itself.
Putting yourself and your own concerns first, to the disregard of the suffering of innocents or the well being of others around you is the type of personal selfishness that typifies classical neutral evil. Shadowheart is classical neutral evil (though with strong signs that she would be otherwise underneath if she were her original self without the brainwashing, and that's showing through more and more with the changes they've made to her), for example.
