Complex sentence: Ruesch did not believe that medical research could benefit by using such methods and, instead insisted that medicine was led dangerously astray by what he saw as pseudo-science, and a fatally false methodology.
Split into simpler sentences: Ruesch did not believe that medical research could benefit by using such methods. Instead, Ruesch insisted that medicine was led dangerously astray by what he saw as pseudo-science, and a fatally false methodology.