Garbage in, garbage out. The term 'soul' is bullshit, so anything that uses the term is also bullshit.

Let's call this what it really is: hate-speech. While the term is nonsense, it does have a societal context where people consider the soul to represent the essence of the person, and people who are disliked, or who commit heinous acts have less of a soul, or are even soul-less (even though that defeats the original concept of soul). Inferring that agnostics lack a soul is equating agnostics to those that society considers to be evil sociopaths. Inferring that agnostics lack a soul lays the foundation to support murdering them. In that context, killing a body that has no soul might not be a crime, because, after all, they're not really human beings. It's pretty much the same line the Germans used on the Jews to rationalize their mass murder.