Agreed. Why would "asthma inhalers" be placed in the same category as proscribed drugs? Presumably if its over the counter or prescription medicine, no intelligent person would have a problem.
In a very broad sense, there's little legal difference between using or posessing a prescription medication that wasn't prescribed for you and an "illegal drug."
Not supporting the above, simply pointing that out.
Strictly speaking you're right. But most people consider the entire picture not just the law, to determine the difference between right and wrong.