Eric asked: I know Scientology opposes the drugging of society, but I am unclear as to precisely what extent it stands in opposition to drug consumption, i.e. absolute opposition vs. nuanced opposition.
What, if anything, does Scientology have to say, for example, about "moderate" caffeine and/or alcohol consumption? Are Scientologists discouraged from drinking beer and caffeinated soda?
The Church does its utmost to not interfere in people's lives. So there are no rules about what you can and can't do regarding drugs - other than the usual laws of the land.
It has been found that certain drugs affect Scientology Auditing, so there are rules about how long you have to wait after (for example) drinking a beer or taking a painkiller before you can get auditing.
The church policy about physical illness is that you should go to a competent practitioner in that field: e.g., an MD, a chiropractor, a nutritionist, etc. At that point it's up to the practitioner.
As to attitudes of Scientologists to drugs, there are some survey results here: Use Of Drugs/Alcohol.
The following data on attitudes to drugs is from my own experience and observations.
Illegal drugs: They are illegal, so we don't touch them.
Legal drugs that have been proven to be safe: if you need a drug because of a medical situation and it has been prescribed by a competent practitioner then you should take it. Ditto for over-the-counter stuff.
Scientologists are individuals. Most that I know are very careful about drugs and we have workable alternatives to them. For example, I'd say a Scientologist was less likely to take a painkiller for the pain from an injury than your average Joe, because we have alternative, very workable methods of handling pain (See Scientology Assists). But if you need a medical drug and it's the usual thing to take then you take it.
Here is an example: a friend of mine had a burst appendix. It was pretty severe and she needed a major operation to handle the peritonitis caused by it (she still has a 6 inch scar from this operation). After the operation she was put on Vicodin for the post-op pain - a powerful and potentially addictive painkiller. As soon as I could, I gave her a course of Scientology Assists and next day she didn't need the Vicodin anymore, she was able to go down to aspirin. After some more assists she didn't need any drugs at all.
Legal drugs that have been proven to be dangerous and to cause harm but are still on the market because the drug manufacturer makes billions from them: We are opposed to these. We don't take them. Examples of this sort of drug: Psychiatric Drug Side Effects Search Engine.
Other miscellaneous drugs such as alcohol, caffeine, tobacco, etc.: Some drugs can get in the way of Scientology Auditing. For example, you can't get auditing within 24 hours of drinking alcohol because it has been found that it will interfere with your spiritual progress. Same goes for some other drugs such as aspirin. So there is no restriction on you having a beer, just that you can't get auditing for 24 hours afterwards.
I've never seen anything regarding most other "minor" drugs such as caffeine or tobacco, it's personal choice.
My own personal preference is to stay away from any kind of drug as much as possible. If I have a physical problem then I'll first try something natural, if it doesn't work then I'll try something stronger, but I'll try to apply the Scientology principle of gradients. E.g., If I had a nasty systemic virus such as Chronic EBV, then maybe I'd start with dioxychlor, if it didn't handle it I'd move on to something stronger and more medical like doxycycline and if that didn't work then acyclovir (BTW: that's an actual example I know of). Of course, all this would be done under the guidance of a competent practitioner, the Church would not be involved in this sort of medical treatment in any way.
I hope that answers your question.