When I was young, one of my Sunday school teachers said the opposite of love isn't hate: It's apathy, the utter lack of concern or compassion. I doubt she realized where that sort of thought would take me. My last Sunday school session involved a different teacher who spoke of Hell with complete apathy for those allegedly burning in it.
Hatred, despite its dangers, is at least understandable. A normal person can understand why someone would hate threats to their or their loved ones' well being. A normal person can understand the desire to take vengeance on something that has already damaged those things. Rage is a natural followup to sorrow.
Apathy, however, often mystifies me. I can understand apathy when it concerns, say, the local sports team rivalries, but not when it concerns the suffering of other people. I've run into countless neocon trolls who don't care in the slightest about non-Americans and their rights. I've encountered countless fundies who advocate apathy as the proper response to injustice. I've encountered some woos who seem almost sub-human or sociopathic in their inability to understand why we want to protect strangers from psychic scams.
Apathy, for me, can be seen as the most subtle and insidious form of hatred. It can stand for extended periods because it only requires inaction in the face of injustice. That inaction also makes it much easier for some to indulge in it. Apathy is a cold emotion, which is probably why I react to it with impassioned flames. What got me to blogging about skepticism instead of just rolling my eyes was the passion of other skeptics. They blogged about how woo hurts people and corrupts our efforts to find the truth. After that, I couldn't bear being silent.