Since you seem to be the spokesman for the "coffee is unethical" camp, I'll direct my reply to you. Escalating the issue/threat that coffee/caffeine poses only serves to downplay the real threat of more powerful and dangerous substances.
First, don't be fooled -- the issue of what constitutes a banned substance is completely arbitrary, and can be nothing else. A "drug" is simply any substance which can be used in medicine. More specifically, a: "natural or artificial substance used as a medication; narcotic, opiate, hallucinogen". This definition can include just about everything, including bananas and Gatorade.
Since the effects of coffee and caffeine are widely known, and anti-doping organizations such as WADA simply are not concerned, and have already addressed this well-known substance, there doesn't seem to be any reason to create an ethical debate, where there is no debate.
You stated that one important distinction is that "carbs" are necessary simply for living, and "caffeine" is not. Au contraire. Your energy can also be supplied by fat and alcohol -- it is not necessary to consume carbs at all, simply to survive. I also recall a story where a WWII POW was able to survive, by eating coffee grounds dug up from the garbage -- i.e. he needed coffee simply to survive. Tragically, his companions did not eat coffee, and did not survive. Coffee comes from a bean, and beans are food.
So how do we decide what is banned, and what is not? The issues that need to be addressed and balanced are:
- Availability and accessibility -- it is no secret that coffee is a stimulant, and is virtually available to everyone. We don't speak of doctors in a secret lab.
- Risk to health or life. Does winning become a life or death decision?
- Fairness - the ethical and moral "spirit" of the rules is to ensure fairness, not to apply the letter of rules designed to disallow EPO, HGH, etc, to mundane substances. Ultimately, the rules exist to ensure a level playing field, and that athletes can win or lose to other athletes fair and square. Otherwise, if it is simply complying to rules, taking PEDs would have the same gravity as high school girls rolling down their shorts -- gasp, horror, shock.
- maybe more...
The answer to this is necessarily and completely arbitrary -- some committee must decide, balancing these (and other) factors, what constitutes fairness. Now whether USADA, WADA, etc., are the right committees, or are doing the job right, is another subject, but ultimately it is a group decision as to what constitutes fairness.
The question to ask, is "Is taking coffee/caffeine unfair to other competitors?" The question has already been asked, and the committee has already answered, "no".
Similarly, your question about injecting testosterone, to jump from 3 to 5 is easy to answer. Would an anti-doping committee reasonably conclude that this practice is fair to competitors? I would say no. It's not about the rule, but about fairness. Unfortunately, since such decisions need to withstand legal challenge, we experience the harsh reality that enforcing fairness (fairly) is not without its problems.