I kicked yesterday some stranger in the nuts and ran away and I don't remember why I did that
Are you sure you cannot recall why you did it?
Ok, well my friends dared me do it, I was drunk
While I'm sure you were just trying to have some fun, which is fine, you shouldn't have fun by doing things like that.  Being cruel is never cool.  Find a different way to goof off!
I don't care
I think you should care what if someone had done it back to you? You know next time you might hurt the wrong person and they could beat you up or something. You should really be more careful and considerate.