My reading of the comment above is that Geothermal uses the same chemical/physical process to fracture the rock and has to dispose of those chemicals afterwards

My reading of the comment above is that Geothermal uses the same chemical/physical process to fracture the rock and has to dispose of those chemicals afterwards (or leave them in place). Fossil fuel fracking needs a continuous supply of the chemicals and a continuous problem of finding a reservoir for the used chemicals so the impact is much, much higher.