Milk consumption makes males taller and broader [1]. So the sheilas want to breed with the tall milk-fed hottie and not his short, weedy and flatulent lactose-intolerant friend.
This is incorrect in its context. While milk consumption does aid growth, lactose intolerance in most cases develops during late adolescence and early adulthood. By that time, most of the growth in height has stopped.
Taking your account as fact (I have no data), this does not entirely refute nikatwork. It may be that in past generations lactose intolerance generally developed earlier than it does now. Today's later intolerance developers are the stubborn residue in the gene pool after the tolerance gene became dominant amongst the children of earlier intolerance developers. The assumption that intolerance was not switched off, but slid back to ever later years could be tested in families of multiple living generations whose intolerance is in flux.
Relevant quote - emphasis mine:
"Primary lactase deficiency is genetic, only affects adults and is caused by the absence of a lactase persistence allele.[9][10] It is the most common cause of lactose intolerance as a majority of the world's population lacks these alleles.[11]"
edit: Also, I can't believe you linked to some forum called "The Straight Dope" as your citation.
Did you even bother to follow the link? Here, I extracted the reference for you [1].
"Chinese and Japanese populations typically lose between 80 and 90 percent of their ability to digest lactose within three to four years of weaning." (Swagerty et al, 2002)
Ergo, lactose intolerance is a factor in children in some genetic groups. Your citation (sourced from the same wikipedia page) does not refute that.
[1] http://www.annualreviews.org/doi/abs/10.1146/annurev.nutr.26...