"If you know electromagnetics and some basic chemistry/biology its simple to understand its harmless."
They also believed the world was flat and electrons flowed positive to negative at one point.
No one who lived near the ocean has believed the world was flat in the last several thousand years. If you have boats you quickly realise what a horizon is and then can surmise that the world must be curved (and probably spherical). RF technicians who work in fields thousands of times stronger than that given out by mobile phones aren't dropping dead from cancer, animal studies don't show anything but the well known heating effects.
The effects of cancer caused by the sun, food preservatives, car exhaust, plasticiser fumes,
oral sex etc are well known and so many orders of magnitude more apparent then any correlation so far found between mobile phone use and cancer. Also with the way things are going you are more likely to die of antibiotic resistant bacteria in the near future then any form of cancer.