In order to discredit materialism you have first to know what materialism ultimately is. I know no Physic that truly knows what materialism is and therefore I have trouble in understanding what spiritualism opposes to and is.
The distinction between subject and object is fading more and more and we all can get back to Parmenides and Heraclitus debate at the source of what Reality is. Change or permanence!
If I had to abstract away to the extreme Spiritus is for motion while Materialism is for Permanence Substance. But even that says very little.
First off in order for something to change it has to have substance so what is it that changes? And when it changes why doesn't it change to something really alien, really out of this reality, why does change itself can only be grasped if what changes goes round to what exists already in some form of another with the same or an otherwise know pattern?
Does the Spiritual Realm has things or only "spirits"?
Does it have abstract objects like numbers or properties?
It has to doesn't it? And if it has to how do spirits ontologically fair in this so called spiritualism?
As I see it it all boils down to substance back again and in that sense Spiritualism is just a fancy word to an alternate form of materialism, supposedly with animism in mind. But then again mind and free will are the ultimate illusion. A REAL illusion. One worth having I grant you that...
In a short sentence:
You see the interesting thing about Phenomena is that they also are Noumena!
PS - The so called great debate between Spiritualism and Materialism if seen from above at a much higher IQ level will definitely seem monkey talk to whatever might be observing. As I write this and rest my case, I stand still and smile.