Original sentence: It has been long established that excessive consumption of alcohol can be toxic to the human body, damaging many organs and cells in the body including the brain and liver and giving rise to a higher incidence of cancer by hindering the immune system
Edited sentence: (But people who believe that lack any serious critical thinking capability and haven't done the basic research available to understand what alcoholism is.) It has been long established that excessive consumption of alcohol can be toxic to the human body, damaging many organs and cells in the body including the brain and liver and giving rise to a higher incidence of cancer by hindering the immune system