Time and time again, the most common stonewall I reach when debating the value of "alternative healthcare" with those idealist of thought and squish of head, is the colloquial phrase "what harm can it do?"

This harm.

The true danger of these "healing methods" lies not in the sugar pills, or the needles, or the stick tea, or the candles, or the stench of the burning rosemary. The true danger lies in the inherent negligence. The impossible claims made by the quacks and charlatans that sustain themselves with such nonsense, make prey of desperate people, who neglect the legitimate medicine or procedures that could save their lives. These crimes are made all the more heinous when the victim is a child who is not capable of making these decisions on her own.

See the reaction of James Randi (of the James Randi Institute).
See the follow-up here.