I don’t necessarily agree with Singer’s points either, but I think Singer is running on the reality that we can really only judge intent when it comes to ourselves, it’s nigh-impossible to judge intent when we cannot know the contents of another humans mind. They can tell us how they feel, but some people are not honest about how they feel, and that can even come from things like social pressure or fear of rejection and other valid areas of feeling that are outside of “I am trying to deceive you for my own gain.” However, despite that, often giving into social pressure or fears of rejection often result in people making decisions that make things worse, not better. Despite the intent, the “deception” still ends up causing issues among a group of people.
So while I agree intent matters, I believe the position Singer is starting from is “with literally billions of humans, it’s impossibly to know intent of all of them and thus makes logical sense to judge by action.”
I think it would be more effective to critique his idea that evil exists as he describes it. Nature, from whence humans came, is brutal and unforgiving and many animals in nature eat their mates or their children for survivals sake. He would call those actions “evil” although they are, in the context of nature, merely survival instinct. In this sense, it’s easier to critique that he is essentially indicting nature itself as evil. Evil is a concept created by humans through our idea of “justice,” which is also a concept humans created. I just think that’s a more thorough way to debunk what he’s saying.
I think it’s an interesting idea to explore, but it doesn’t mean we have to agree with it.