I'm often criticized for giggling when people say "it's all natural" because I do it, admittedly, when the statement is otherwise a valid one to make. (ie. "Eat product X - it tastes great and it's all natural.")
The word "natural" comes up often when people refer to items in alternative medicine, personal care, food supplements and even when people speak about certain types of food, etc. "Natural", however, needs to be understood.
Suggesting "it's all natural" is a silly position to take (which is why I must giggle at it). Let's look at other things that are natural: mercury, arsenic, poisonous mushrooms, botulism bacteria, and countless other things found in nature. Other things that are natural include hurricanes, earthquakes, tornadoes and floods. I'm not sure I'd argue that since it is natural it is "good" or "safe".
"Here, drink some mercury, it's all natural!" would be an absurd thing to say which, in turn, makes the "it's all natural" a horrible argument.
It's the dose that makes the poison, however. Paracelsus once said, "All things are poison and nothing is without poison, only the dose permits something not to be poisonous." In keeping with that, simply because something is "all natural" does not make it safe to consume/use without regard. Similarly, something that is poisonous at higher dosages may be beneficial (healthful, even) at smaller doses.
The next time someone says "it's all natural", remind them that feces and urine are natural too. In other words, "natural" is no argument for or against any alternative medicine or food supplement.