The thing they cry out against is not Socialism but a phantom of their own imagining.
Another answer is that 'The Philanthropists' is not a treatise or essay, but a novel.

My main object was to write a readable story full of human interest and based on the happenings of everyday life, the subject of Socialism being treated incidentally.
This was the task I set myself.

To what extent I have succeeded is for others to say; but whatever their verdict, the work possesses at least one merit--that of being true.

I have invented nothing.

There are no scenes or incidents in the story that I have not either witnessed myself or had conclusive evidence of.