One wonders here if the determiner the is missing before “foolish traditions of your fathers”. If traditions were not postmodified by the prepositional phrase “of your fathers”, then the current reading would be perfectly fine (“behold they are foolish traditions”). Elsewhere we consistently get the in expressions of the form “tradition(s) of X” (34 times), including these nearby examples in Alma 30–31:
The original manuscript is not extant here in Alma 30:14 for the first part of “foolish traditions of your fathers”, but the short spacing between extant fragments does not allow for a the except by supralinear insertion.
The text here in Alma 30:14 (“behold they are foolish traditions of your fathers”) is different from all other occurrences of “tradition(s) of X” in that it is the only instance where the noun phrase “tradition(s) of X” acts as a subject complement. The subject here is the pronoun they, which refers to the earlier noun phrase “these things which ye call prophecies”. In other words, the sentence “these things which ye call prophecies … are foolish traditions of your fathers” works well enough without the the before traditions. Note that neither traditions nor prophecies takes the definite article. The critical text will therefore accept the unique occurrence here in Alma 30:14 of “tradition(s) of X” without the definite article.
Summary: Maintain in Alma 30:14 the unusual but apparently intended reading “behold they are foolish traditions of your fathers”—that is, without the normally expected definite article the before traditions; in this instance, the larger context allows for the indefinite use of “tradition(s) of X”.