Is revenge OK?

[Reader]

Originally Posted by J. Mason

I am in favor of the death penalty but believe in revenge when needed.

But again that is just my opinion!

I wish I could express myself better on this, but, I wondered if there was an actual scientific, or non-emotional, reason to be against revenge and cruelty, etc.

Like, could someone convince others, using nothing but logical debating skills or science, why revenge or cruelty is "wrong". For example, to my knowledge, animals do not partake in revenge, and they do not seem to particularly be involved in intentional cruelty. Why?