I'm always amazed when people feel the need to say to the world what they're thinking, especially when it is personal, and when the situation is controversial l

I'm always amazed when people feel the need to say to the world what they're thinking, especially when it is personal, and when the situation is controversial like this. Is there anything to be gained, reputation-wise or any other way, in coming out and saying (paraphrased) "hey I know this guy and let me tell you he's a two-faced jerk"? Is this just attention seeking?