That article is a perfect example of a highly dubious source. The experts are one nutty doctor who claimed that milk can lead to juvenile delinquency (), and then mostly a bunch of "alternative medicine practitioners" (a chiropractor? Really?) and cherry-picking studies while distorting their actual conclusions. For instance, it states:

A 1992 report in The New England Journal of Medicine also notes that cow's milk can contribute to juvenile diabetes and autoimmune diseases by impairing the ability of the pancreas to produce insulin.
The actual paper noted a correlation between components of cow's milk and diabetes. That is only one step in the scientific process for determining causation. Also note that the paper cited is over 20 years old, and that is the most recent paper cited. The article also makes no mention of studies that reached the opposite conclusion. And more recent studies show that children who avoid cow's milk altogether face their own health risks unless their diet is balanced out to get the beneficial nutrients from other sources.

There may be some potential negative consequences to little kids drinking tons of milk. But there are unquestionable benefits for those kids having milk and getting plenty of calcium. If you want to be safe, having limits on milk and having other sources of calcium in a child's diet may be the way to go. But I have yet to see much in the way of persuasive evidence that milk is something to be completely avoided altogether.