First a couple of facts: it's nothing at all like birth control, neither of the reasons presented is the reason why there is no birth control pill for men, and there are methods for male contraception. Use is another issue, but that's true with everything. But most importantly, let's talk about fish
With regard to whether or not there may be a random herb that could, in theory, be a reef-safe cure for ich: Sure, why not? A few examples of random herbs giving us medicine we use in people:
Digitalis -- one of the most widely used medications for atrial fibrillation today and the original cure for a disease called "Dropsy" (now known as congestive heart failure) was introduced in 1785 by William Withering. It comes from a plant called "Foxglove," the extract of which was long known to be a highly effective poison and was used in the middle ages as a means to determine guilt or innocence by divine intervention in the now infamous "trial by ordeal" system.
Colchicine -- a highly potent anti-microtubule drug extracted from the autumn crocus and is known today primarily for its use in acute attacks of Gouty Arthritis. Reports of the use of this plant for the treatment of such conditions date back to ancient Egypt.
Aspirin -- Widely regarded as a boarderline miracle drug for its ability to improve heart-health and anti-inflammatory action, this drug has been in use in it's herbal form since before the common era. The most commonly known natural source is willow, but there are other plants you can get it from. The ancient Egyptians knew about this one too (My gosh were they cool).
I guess I'll get to the point. The standpoint that we normally take in this argument is that just because someone reports a natural remedy to work doesn't mean it actually did (correlation does not equal causation), but the opposite statement is equally false, as correlation
might equal causation. Considering the origins of many of the medications that we use, we should not be so quick to dismiss claims that have not yet been adequately investigated. All we can say is that they aren't known to work (unless of course they have been investigated and shown to be ineffective).
This does not mean that we should snub our noses at what is already known to work (e.g. QT and copper). Indeed, that is the route I would take 100% of the time in my own aquarium barring a future discovery. But, reports such as this one, although not scientific and purely anecdotal, are not entirely without value. I guess my point is we shouldn't be so quick to disparage what we don't know. Whether or not it's the best action to take when we have things we know to work is another issue entirely, but the idea that ginger can't work simply because it's herbal is a bit presumptuous.