Whenever anyone demands “objective evidence” for historical questions you know your dealing with a hermeneutical and epistemological misunderstanding or naiveté. History–in the sense of the actual human past–does not exist. It cannot be directly observed. You cannot experiment upon it by giving Napoleon an extra division of infantry to see if he could win the battle of Waterloo. History is a non-empirical discipline. And anything that is non-empirical cannot be objective. There is, of course, in the study of the philosophy of science, a significant debate as to the degree to which even empirical and experimental disciplines can be “objective” but that is a different question. Be that as it may, history, clearly, is not empirical. Thus, the demand for “objective evidence” represents a fundamental misunderstanding of both the nature of the human past, and our ability today to understand it.
When turning to the Book of Mormon, there are at least four layers of interpretation that one must undertake in trying to understand the questions of the historicity of the Book of Mormon.
1- We must correctly interpret the Book of Mormon. This is, of course, the fundamental problem, since many of those critiquing the BOM have either not read the book, or have read the book in a completely superficial manner, and furthermore, are not familiar with how modern LDS scholars of ABMS understand the text. It is pointless to argue against an interpretation of the BOM which no LDS scholar believes. (Note, there are also many non-professional LDS interpretations of the BOM–the Heartland Theory for example–which must not be conflated with scholarly LDS studies.)
3- We must correctly understand and interpret ancient Near Eastern evidence. Essentially the same issue as #2 above, but with a different data set. This has been a more fruitful path for BOM scholars, since there is far more evidence from the ancient Near East than from Preclassic Mesoamerica.
4- We must attempt to understand the possible relationships between scholarly interpretations of the Book of Mormon and the Mesoamerican and ancient Near Eastern data. This final phase–the most important and difficult one–can only begin once phases 1-3 have been conducted. And note: only LDS scholars have engaged in all four phases of interpretation. The methodological and hermeneutic imperative is that we engage in all four phases if we wish to discuss the question of the historicity of the Book of Mormon.