When I have failed to acquire enough personal experiences to make up my mind one way or the other on something as scientific (or at least potentially scientific) as practicing medicine, I defer to scientific consensus.

Found your problem. Here's some serious, take it at face value pragmatic rhetorical advice:

When you have these conversations, your counterpart has already rejected scientific consensus.

Not saying they've rejected it correctly. Not saying they've rejected it rationally. Not saying they've even rejected it calmly but the fact of the matter is, you think you're saying "double blind testing" but they're hearing "one plus one equals three BELIEVE IT INFIDEL." It will get you exactly nowhere. It will escalate things from dispassionate to ad hominem. And it will read, as it was surely intended, as a dismissive attempt to silence dissent.

If you wanna get people back to "scientific consensus" territory you need to figure out where they stepped off the path first. For some people, it may be way the fuck back - my wife worked with a woman who rejected germ theory. For some people, it may be in the weeds - yeah, there have been a couple studies that insist echinacea does fuckall for colds, but nobody with a clue recommends echinacea pills for anything and they sure don't recommend them for colds. On the one hand, you're pre-pasteur. On the other hand, you're arguing about research protocols. In neither case does "dismissive" open a dialog.

Arnica works best when you put it on immediately. I'm about 98% of the way to chalking that up to placebo effect, but I'm also the kinda guy that will gleefully leverage the placebo effect whenever possible, even on myself. Especially on myself.

CureZone sounds like a frightening place. There's some truly batshit stuff out there, and "it gets worse before it gets better" has a long and storied tradition.