I believe for proper clarity that the time period in which this myth was supposedly originated be mentioned in this article as taken from the cited writing which discredits this myth.  Simply stating that it has been illegal since the 18th Century to beat your spouse opens up questioning as to laws before this time.  However, the article cited makes mention of the colonial time period being the origins of this myth.

Essentially in this case, lack of proper quotation is lack of proper evidence making this section incomplete and partially invalid.