Our society tends to regard as a sickness any mode of thought or behavior that is inconvenient for the system and this is plausible because when an individual doesn't fit into the system it causes pain to the individual as well as problems for the system. Thus the manipulation of an individual to adjust him to the system is seen as a cure for a sickness and therefore as good.
Psychiatrists look for twisted molecules and defective genes as the causes of schizophrenia, because schizophrenia is the name of a disease. If Christianity or Communism were called diseases, would they then look for the chemical and genetic “causes” of these “conditions”?