Also, you sort of seem to be basing this around people who believe god individually created each species—one by one—as written in the book of Genesis, even though Genesis left out a few hundred million species of animals and plants and insects and even microbial diseases. What if God just created existence? Since there can be no happiness without sadness, no pleasure without pain, life without death, existence of any of them requires the existence of the opposite.
The point was that killing isn't necessarily "evil". Perhaps it wasn't quite on point. There have been wars that killed millions of people, and even though I don't think they were pleasant or good, I don't think all the killings were necessarily "evil".Which would be a brilliant observation were the diseases in the OP discriminatory, and only affected murderers, rapists, sociopaths, and criminals. However, since they do not, your "some killing isn't evil" argument is irrelevant.
Do you think the bacteria are evil because they kill people in their selfish pursuit of reproduction?