Those „some“ say God, yet talk about the Devil. How could a loving and merciful deity create a world where it‘s creatures need to eat up each other for surviving. Often they have to die slowly and painfully. Your disease and desaster theory works only partly, as many species which went extinct did so due to a little rock some „God“ forgot amid it’s omnipotence. And the millions of indigenous people of America, which got only killed because of a handful of white people. Some say God, I say nature. But neither is an excuse to justify pain and death.
A horse which dislikes it‘s owner because of bad treatment won‘t even come for an apple but hide.