"I want to know why are people bothered about how much radiation this device gives out, but don't think about how much EXTRA radiation they receive when flying in an aircraft?"

Maybe they are.

"I am guessing people don't know they are receiving larger than ground level radiation doses of radiation when cruising at altitude."

In many cases, that guess is wrong.

"maybe its because they are safe, just like this scanner!!!!"

The scanner has a low risk. It doesn't mean it is inherently totally safe. The risk of getting cancer from one of these devices is approximately the same as being killed in a terrorist attack on a plane, so using the same reasoning, we can say that flying is safe and therefore, the scanners serve no useful purpose.

"But I don't see any news stories about radiation at altitude due to solar flares etc..."

Maybe because that is an inherent part of flying, rather than a deliberately introduced risk.

The simple fact is that these devices will take more lives than they could ever possibly save and anybody who supports them is an idiot.