If science is not based on observable evidence, then it is only a theory. If an experiment has flaws in it or is based on bad assumptions, then the conclusions cannot be relied upon.
The Terrain And Germ Theories
The Terrain Theory states that ill-health is caused by poisons in our environment, such as air pollution, radiation, synthetic chemicals, pesticides and lack of good nutrition. The Germ Theory states that ill-health is caused by dangerous bacteria and viruses. If a certain type of bacteria, labelled as dangerous, is found on most people, is it really that dangerous? Or is the source of ill-health something else? Are bacteria friends or foe? Do they clean up after another problem causes damage? Are both theories partially correct?
We are told the immune system kills virally infected cells. If a certain virus does not directly cause the death of its host cell, how does it become more pathogenic? Some viruses have been identified solely by analysis of genetic material. How similar is our genetic material to these intracellular parasites?
What about bacterial viruses (phages)? What is their role? Spreading genetic information? Killing off bacteria when there are no more nutrients for them?
What was the cause of the polio epidemic in the 1950s? Why was the pesticide DDT banned?
What was the cause of the 1918 Spanish Flu Pandemic? A virus? Bacteria? Something else? Where did it go?