You wouldn't need scientific proof that most people wouldn't eat shit either. It's a reasonable assumption given that after all their analysis, meetings, debates etc their solution is to dump it into the ocean and not for internal consumption. This move is bad for their international pr, so logically if there is a better/more accepted option they would have chose it. Unless you are telling me that this decision is more likely made in vacuum and the decision makers are not very smart.

Great so maybe Japan should use that water for internal consumption then? Obviously they won't do that, so can't complain when other countries are uncomfortable with it.