The world is full of pain, death and suffering - and that's not just factory farm animals.

War, famine, natural catastrophe, discrimination - it's just all so common.

Why, if there is a beneficient god?

My sentiments, exactly. If there is a good and all powerful "god," then I hereby say to him or her "EXCUSE US, BUT WE COULD USE A LITTLE HELP DOWN HERE!"

Why is there indeed all this hate, negativity, abuse, violence if we were in the hands of a benevolent and kind god?

The question remains and is definitely a question that is not mundane. It, I feel, ultimately points to the actual existence of such a god, and if this god does exist, then why are the consequences of having this god result in death, misery, natural disasters, etc? Are we in receipt of a malevolent god?

That logic doesn't disprove Zoroastrianism. Maybe there are two deities who are warring; one is evil, one is good. Maybe the reason the world is the way you describe it is because the evil deity is gaining the upper hand.
Also, maybe there is a deity that recognizes that without pain we could not stop pain, that we would not grow back faster without being cut down.