I once heard an interesting sermon about how claiming that god is good is wrong. The church talks about the trinity, this massively complex way of describing god, since his true nature is beyond human comprehension. But people also attribute god with this simple, human concept of goodness. How, if we can’t understand god, can we say he is good, or that he has any human qualities? The priest’s answer: we can’t, and thus shouldn’t.
At least we kill them instead of prolonging their suffering.