I just don't understand why people don't want to know. It's like opposition to fast food restaurants showing nutritional information on the menu...
There's the primary issue that we debate on this topic which is the health scare / concern. IMO, that's what this thread is mainly about, and is what is present in OP. From this position comes a key secondary issue in this ongoing debate which is (as noted in OP) that no vendor should be selling this, as it is an avoidable risk. This stems from the Dr. F. statement (of opinion).
The primary issue and the key secondary issue really ought to be scrutinized with as much gusto as all the other things that are thrown against the anti-vaping wall in hopes they stick and scare people away from the "dangerous" activity that vaping is believed to be.
Another secondary issue of great significance in this ongoing debate is whether vendors ought to be disclosing this information. Some anti-diketone types will claim "this is all we are after." I somewhat believe this, but mostly see it as moving the goalposts from what is the primary issue. I think these types have reconciled with themselves that it would be a very bad thing to suggest all vendors must be mandated to get rid of this compound, and so go with what they feel is politically correct position of disclosure.
The reason there is opposition to disclosure is really only based on scope of mandate/request. IOW, are you saying the political position for vaping community ought to be mandatory disclosure? Or are you saying you will personally only seek vendors in the current (under regulated) market who match up with your version of disclosure? If it is the latter, then I think those of us who show up as debating this issue with what appears to some as diketone denial, would not, even a little bit, resist that effort. Perhaps even engage in the same effort, as if we are not actually diketone deniers.
But if you are arguing for the former, and that it ought to be a mandate for all vendors to disclose, then you are arguing for what the FDA deeming was partially (to mostly) about. Difference for FDA is that while this is current pet issue within vaping community, FDA would just assume mandated disclosure on all ingredients, and that FDA take on responsibility of middle man. Thus, not that consumers would actually receive full disclosure (though they might if vendor wishes that), but FDA would receive full disclosure and then either allow it on market or reject the application (for possibly one or more of a million reasons).
The other significant aspect of disclosure is that it is entirely unlikely that vapers will all be on the same page with what that means. Let's say all of us discussed this and magically we were all on the same page for what disclosure means. I highly doubt that would occur, but let's just accept the hypothetical. Then let's say us 50 vapers on the same page encounter 250 vapers who say our version doesn't nearly go far enough and another 1000 vapers who say we are demanding way too much in terms of disclosure. Who's right in that situation?
FDA is going with as full of disclosure as humanly possible, on all things, and making it a mandate. I think a reasonable case can be made to say that is the safest path forward. I think the pro-vaping perspective assumes that to be a most foolish path going forward because a) it'll cost someone (likely consumers and industry) a lot of money to stay on the market and b) it might actually not lead to more safety. Especially considering that there are really no known incidents of serious harm to vapers from inhaling the ingredients. Which is why I long to wager with anyone who thinks we would be more safe under FDA final rule. The path that is intentionally aiming for across the board, full disclosure that is heavily mandated.