I suggest that you read Judge Leon's 32-page Opinion document carefully. You can download it from the CASAA site:
CASAA Smoking Everywhere vs. FDA
It's the link, "SE vs FDA Opinion".
Judge Leon specifically addressed the issue of whether the government is permitted to regulate products as a drug if anyone other than the vendor / manufacturer makes a health claim. The Answer is "No."
The key issue of whether any item can be regulated by the FDA as a drug is the products' intended use. The intended use is determined by the seller, not the buyer, not by scientific researchers, not by forums, and not anyone else. The seller would have to be making health claims.
So there is no slippery slope here. The Federal Courts have spoken and there is no danger that the FDA will appeal the decision. If you had followed the case closely, you would have seen that as far as this case is concerned, all appeals, except for the Supreme Court, have been exhausted.
A different court, however, is the court of public opinion. The opponents of harm reduction want to be able to claim that smoking and vapor are the same thing--and they are both bad.
The public needs to understand that the availability and promotion of low-risk alternatives is saving lives. The public needs to understand that these products are such an acceptable substitute for smoking that many of us are no longer endangering our health and shortening our lives by inhaling smoke.