I've found one of the issues of discussing philosophy is that context matters so much. Every question and answer assumes other answers, and leads to other questions. The interconnectedness of the field limits the use of individual discussions then. That's the entire basis of Descartes foundationalism with "I think, therefore I am": find the most basic assumption that can be made.

In order to really disprove the existence of evil,

Another issue the existnecer of evil shares with the existence of God is burdern of proof. Do we have to prove evil doesn't exist, or do we have to prove evil does exist? Like I said, just more questions.

I'm not sure I agree that we need evil to avoid trivializing tragedies.

I meant that to be a part of my point, but I ended up eating supper while writing the post and so maybe it isn't as well written as it should be. I think baitedcrow got at this some too by saying that we use evil to dehumanize perpetrators. Honestly to me, that seems to trivialize tragedies more by blaming them on an 'other' and not acknowledging the human facet. Yet when I've seen "evil doesn't exist" voiced, the response always seems to be that people have experienced tragedies, and that saying there is not evil is almost rude to them.like saying what they went through wasn't all that bad. Yet I think we can all pretty much agree evil must be something different than just wrong actions.

Suppose a meteor crashes into a small remote town, killing everyone. It's a tragedy, but we wouldn't say that the meteor was evil.

At risk of sounding dogmatic, I want to mention another point of Sober's. He divides evil into two categories: human evil, and natural evil. Within the context of the Argument from Evil (an all-powerful and all-good God cannot exist alongside evil), both seem to work. But I agree with you, the concept of evil I'm familiar with has a definite moral part. A meteor has no morality, and therefore cannot be evil. Honestly, the more I think about it, the main failing of the Argument from Evil is the use of the term evil.