Curezone has a survey of the many people who have safely done these flushes and all the possible dangers which are rare are discussed in the introduction and explanation sections!
The only reason it is safe is because the vast majority of the people doing these "flushes" do not have real gallstones. So there is nothing to possibly get lodged in the bile ducts. If they had real gallstones then there is a great risk. But as has been shown over and over the green blobs that people are passing are primarily saponified olive oil, which there is no risk of passing since they are formed in the intestines instead of the gallbladder.
Life has its dangers, are you going to stand in the street all day and night warming people they may get run over by a car if they cross it???
So if you see someone in danger you are going to do nothing? That is what I and some other people are doing here. We are warning people that may have real gallstones of the potential dangers. If someone still goes ahead and injures themselves in the process then the only person they have to blame is themselves.