Because it leads to dismissal of actual medicine. Too many people believe homeopathy is a valid method of treatment, many of those people would go homeopathy first GP second. People actually die by doing that.

Given the nature of dilution than a little bit of many, maybe all, diseases exist in water to the same levels of homeopathic cures.....so normal drinking water should cure everything rendering you invincible to illness! That is if homeopathy worked which of course any sane logical person knows it doesnt.