I sort of agree.
You have to define "Soul" first before one can answer that.
He is a machine, yes, but so are we, just different material bodies.
We have a brain that produces our personality and so does Data.
From what I understand of his positronic matrix is, that it forms new neural pathways all the time and makes his brain as unique as every human's.
I think they had a diagram of it up in one episode.
Of course that is abit of sci-fi magic, but within the StarTrek universe that Data really is much more than a programmed automaton.
As much as we are anyway.