I don't think that it's an error, in fact the argument he is making about minimum wage exists in a world without a state provided safety net.
The main argument he is making in the book is that economics is a complex system and is hard, and that we always need to look at the forgotten man. Those that think policy decisions are simple - have a minimum wage or not - will cause a whole host of unintended side effects as your post describes.
The main argument he is making in the book is that economics is a complex system and is hard, and that we always need to look at the forgotten man. Those that think policy decisions are simple - have a minimum wage or not - will cause a whole host of unintended side effects as your post describes.