And furthermore, lots of people are really, really dumb. I got an A in honors high school chem and that was only five years ago, and I had to visit Wikipedia to check every word more obscure than "solution" in that description of saline - the average patient probably did worse or didn't take the class at all, took it longer ago if they did take it, and remembers less. Heck, there's probably a scarily high percentage of people who wouldn't even understand you if you told them it was saline.

Now there is an interesting question: can you be held morally responsible for lying if you just don't have the time/patience/ability to explain something moderately complex to someone really stupid? What if they don't even know the word "placebo" - then what do you do? Explain scientific controls and psychosomatic effects while you're trying to extract a bullet, or what have you, from your patient?