After 39 years of trial practice as a lawyer, I also assume that people treat me the same way I treat non-fiction books.
Now we find ourselves surrounded by a huge international genealogical community. Substantial parts of that community consist of people with only the most casual and superficial interest in genealogical research. They are easily satisfied with a few facts about their "relatives" or ancestors and have no intention of pursuing any research. This group would be surprised that anyone would consider them to be genealogists. At the other end of the spectrum, we have professionals who spend the most of their time in intensive, detailed research into original source documents and fuss about the details of formatting entries. How do we reconcile this disparity? Out of this huge mishmash of data do we determine what is and what is not reliable?
Unfortunately my rule regarding non-fiction books is of little help to me in evaluating genealogical research. Of course I can detect blatant errors such as mothers whose children were born after she is reported to have died, but how do you detect less obvious, unreliable genealogical conclusions? More importantly, that same entry with the obvious data error may otherwise be perfectly reliable. Presently my only conclusion is to redo the research and come to my own conclusions. To take this position I have to begin with the assumption that every undocumented assertion is questionable. Then if the documented assertions are reasonable and consistent, I can then decide whether or not I will adopt them and rely on them after I have reviewed the documentation.
The basic flaw in such schemes as the "Genealogical Proof Standard" is that if the researcher gives, what appears to be, complete, accurate source citation for each conclusion and writes a report that seems to comply with the standard, then you are still in the situation of relying on the researcher's integrity. Despite the adherence to formalities and despite reputation, from my standpoint, I would have to personally verify the conclusions. All of the citations and "arguments will merely make my job harder or easier depending on the availability of the sources cited. However it is the nature of historical research that two or more researchers can look at the same source documentation and come to completely opposite conclusions. Even if the entire genealogical community is in agreement on a particular issue, subsequent research may disclose differences. See the Thomas Jefferson controversy for example in the following book.
Gordon-Reed, Annette. The Hemingses of Monticello: An American Family. New York: W.W. Norton & Co., 2008.
The important issue here is that the source citations and documentation exist so the conclusions can be checked. When I become disenchanted with a book, it is usually because there is a lack of documentation for the conclusions expressed. In the case of the example above, there was no evidence that the writer had based his statements on any cited authority. If the author or researcher is expressing an opinion, derived from experience or contemplation, that is fine. But if you tell me that your opinion on a historical or genealogical question is a "fact" and that the fact is proved by some source, you had better tell me your source.
If I enter information into a pedigree or family group record for my own reference and continued research, then what I have is my own business. But if I take that same information and add it to an open online family tree, then the information become everyone's business. Individual records from the distant past to the present, are essentially claiming to be correct. Even leaving aside the issue of intentional fabrication or lying, original records are assumed to be correct unless contradicted by other records. For example if I find a birth certificate for my grandfather, I am justified in assuming the date recorded is correct unless I find another document that contradicts that same information. If I further assume that I have found five different records that have a birth date for my grandfather and none of the five agree with any of the others, then I must either approximate the date or choose the one I think is correct. In either case I need to show all five records with the five different dates in the explanation for my conclusion. The case where a given date or event has contradicting source records is fairly common. As long as subsequent researchers are provided with the contradicting information, there is no problem. The actual date is still unknown or unsupported.
Even if an immensely knowledgeable researcher were to follow all of the recommended guidelines for "proving his or her conclusions," the bottom line is that the conclusions are nothing more than a vaulted opinion. One example of what I saying comes from a situation I wrote about previously. My Parkinson family line initially had a long list of sources for more recent ancestors. However, despite the long list and the apparent detail of the entries in the FamilySearch.org Family Tree, there were no sources cited for any births, deaths or marriages. The citations demonstrated more than adequately that the family lived in Utah but there was not one citation showing their origins in England.
The challenge we face, when you analyze all the factors involved, is that we can only make progress in finding our ancestors with any chance of reliability by carefully drawing our conclusions from the existing historical records. Once the information has moved into our "comfort zone" we can then extend our lines even further. But like the situation when I am navigating around an unfamiliar neighborhood, there is always the chance, despite using GPS and maps, that I will take a wrong turn. Likewise there are many wrong turns in genealogy.