It is almost impossible to prove a negative .We can't prove that aliens didn't build SH , or the tooth fairy doesn't exist . To argue against either is not being disrespectful . Phrases like like closed / open minded , thinking out of the box, standing to reason , it's only common sense etc are meaningless . When giving an opinion you use your mind to the best of your ability not accept anything and everything without question or ignore the facts , or not reason .

There are countless explantions for something like dowsing "working". Anything that a dowser claims to do can be done by non dowsing means whether "finding " water or anything hidden , people do it all the time and don't attribute it to a special ability .
When put to the test dowers don't perform any better than expected by chance .
Non dowsers find archaeological sites , monuments etc in areas where there has been no recorded or obvious archeological sites , dowsers don't , but are for ever claiming the ability to do so .