That has nothing to do with what I'm saying. If you invest in a company that "only" has IP, your invested cash itself is still part of the company's assets, so it's not like you're buying shares of vacuum. If the company liquidates itself - you get back your proportion of the company's assets. The situation is not the same with Bitcoin.
Yeah, it certainly has similarities to an unbacked currency. I wouldn't personally call it "fiat" currency (unless you think El Salvador making it legal tender makes the difference here), just some sort of unbacked digital currency. The IRS's characterization of it as a virtual currency seems like an accurate description to me (as I'm guessing it is to you) - and the SEC refusing to consider it a security also makes sense to me (for all the above reasons I've been trying to explain to the others here).
"By arbitrary decree" was the meaning I meant. Someone declared it to be a currency, it need not be a government doing the declaring. But yeah, we're basically in agreement, that's the underlying problem with crypto, it's a fiat currency (no intrinsic value) traded like it's a security (which usually has some even if very abstract, intrinsic value).