From the outside it all looks rather perverse. The developers have started discussing an imagined security threat, rather than simply considering that it might be worth keeping the feature because users appreciate it. If they have considered that and still decided that the feature is to be dropped, there isn't anything more to discuss unless someone wants to pay for it.
When it was announced that Firefox 64-bit nightly builds on Windows would be discontinued, I stopped using them and dropped back to Waterfox (a third-party Win64 build) instead, which is usually a bit behind the latest upstream release. But I wouldn't expect the Firefox developers to take the slightest notice of that as some kind of threat to the Internet. They can just produce the best software and then it's up to everyone else whether to run it or not.