At a holiday park with my teenage daughters. The lodge is right by the beach and we were having a pre-dinner walk along it. We came across a dead and rotting seal on the sand ... unfortunately I didn't notice it in time to stop the dog from rolling on it, but that's another story!
Anyway, on the way back, we saw some children throwing stones at it. I was really saddened by this but couldn't explain why. It's dead, it's not like it can feel anything.
And then I remember feeling this way as a kid myself, when I saw kids throwing stones at (well, kind of 'into') dead jellyfish on the beach.
I can't articulate why it bothers me so much, I just know it does.
I should add that, as a child especially, I much preferred animals to humans 