The term sinat chinum is usually translated as baseless hatred, yet what does that term even mean? Is hatred ever baseless? While we can argue that a reason for the hatred is problematic, foolish, even unjustifiable, can we truly apply the word "baseless"? There always is a reason, even if we think the reason is wrong. Furthermore, can one really state that the hatred that emerges in the famous story of Kamtza and Bar Kamtza is baseless? I think that, while I may strongly disagree with,how the person dealt with his negative emotions, there was reason for why they developed.
For all these reasons and more, I have chosen to translate sinat chinum as purposeless hatred, in other words hatred that is not acted upon correctly. We all develop negative emotions; the question is how we respond to these emotions. The response to hatred may not be to simply declare that it should not exist but to respond to the hatred correctly. To make this emotion, in the end, serve a postive purpose. Sinat Chinum is when we just allow it to exist and not strive to serve this purpose.
I invite you to read more about this in my two part essay Defining Sinat Chinum at
Rabbi Ben Hecht