Those are just strawmen, though. Where do I say morality is just "defined," as in arbitrarily stipulated? I say that only on atheistic naturalism can morality have an objective basis as well as a subjective one. Morality evolved in social mammals as empathy, an instinctive desire for fairness, a fear of psychopathic tendencies, and so on, so it's not a mere arbitrary stipulation.

Unnecessary suffering is excessive, meaning that it's more than would be accepted under civil conditions. Suffering in the wild is often excessive since it's unconstrained by moral rules and civil laws. Wildly generated suffering can be excessive in that it may be more than a polite society would accept. We'd try to end such suffering if we could. That's what palliative care in a hospital is for, for example.

You can say that even wild suffering is necessary in that God has a reason for it, but that would be an empty appeal to mystery, and we'd still be left with the appearance of an excess.

The notion that atheists have a "belief in nothing" is another strawman. That's like saying all atheists are nihilists. Instead, most are naturalists and humanists.