Thanks for writing, although it’s a tad off-topic. I can't cover everything in that article, and it was responding to a Christian. For what you are asking, the issues are explained in Bomb-building vs. the biblical foundation and What is ‘good’? Answering the Euthyphro Dilemma).

I would turn this question around and ask, why, under an evolutionary world view, should harming another be considered a bad thing? Isn’t Darwin’s “war of famine and death” about who harms something else before it is harmed by that something else? More specifically, two evos claimed that rape is a good evolutionary strategy to help men spread their genes, and one was tied in knots trying to explain why it was still ‘wrong’ (see Rape and evolution).

Also, why is slavery so wrong, given that some species of ants enslave others, as Darwin noted? Conversely, while slavery was ubiquitous, it was abolished only in the Christian world, led by people who would now be called the ‘religious right’ (see Anti-slavery activist William Wilberforce: Christian hero).