[brraverishhh]

The banana equivalent dose is dishonest for several reasons:
1) Banana radiation comes from an isotope of potassium which occurs uniformly throughout all terrestrial potassium. Through homeostasis, the human body maintains relatively constant levels of potassium and thus the radioactive potassium isotope as well. Key point: you cannot raise the level of radioactivity in your body by eating bananas nor other potassium rich foods, at least not for more than several hours, rather you excrete the excess. This is not the case with other forms of radiation, see below.
This is the main way the banana "argument" is dishonest and disingenuous.
2). Potassium 40 (the isotope) also has a long half life in the billions of years. The qualitative aspect of this type of radiation is low. An equivalent level of strontium 90, say, is much worse for the body.
Unlike potassium 40, other nastier isotopes (iodine 131, cesium 134/7, sr 90, etc) can and do accumulate in the body. It isn't so much a single dose with these nasties that hurts, but rather how the biological concentrations increase with time and exposure. Bananas do not give one this kind of accumulating dose, see 1 above

tl;dr. Banana equivalent dose is dishonest. I can eat bananas morning day and night and not increase the amount of radioactivity in my body. If I drink Fukushima groundwater morning day and night, the radiation accumulates and will almost certainly kill me in the long run.