That could very well be a lot of it, but you cannot discount potential empathetical fallout. Like you said, you've known for quite a while. But when you read the actual accounts, know the statements, smell the sink at the sites, see the wreches, it can be a little overwhelming.

Somewhat related, people who watch horror and zombie movies make me laugh. It is different when you get to the real thing. A bunch of those film buffs won't be as desensitized as they wish they were.