The fact that some inflation is beneficial clearly is the commonly received wisdom, including by whatever experts I could find; I couldn't find
any trustworthy source arguing the opposite. A casual dismissal of inflation being necessary is therefore warranted - at least unless there's some extraordinary level of evidence provided, or if my skimming of publically available opinion is somehow wrong (sure, could be!). It's the official policy of the Fed, for instance.
Additionally, note that the money supply is ever growing - faster than inflation because the economy is growing. Now, there are apparently extra factors to consider here, including concepts like the velocity of money, which mean that money supply isn't trivially linked 1-to-1 to the economy's expansion and inflation. I'm no expert on the matter, to be clear, but that's my impression trying to search even for refutations of that stance - if your impression of commonly held expert opinion is different, it'd be interesting to compare links to check whether our media bubbles differ somewhere.
We cannot rule out that stablecoins might serve us well. But just because we have imperfect information does not mean all possibilities are equally risking; the risks from conventional monetary policy (including variations such as modern monetary theory) are simply much better understood because we have examples and history to learn from. The original article makes the case that stablecoins aren't really all that novel as a financial instrument (even though their technical underpinnings might be), and the argument appears sound to me (a non expert) and the source reliable (with a reputation at risk were their analysis clearly wrong).
As such, why should we ignore risks we understand, and take on additional risks we don't understand? At issue here isn't really the fact that it's a cryptocoin, but rather how it functions in the financial market. The article explicitly calls out that the technical implementation may have benefits, and a knee-jerk ban could be overzealous.
The issue is essentially financial, not crypto related, and I don't see any clearly open questions that might argue for allowing unregulated stablecoins, let alone a refutation of the premise that stablecoins have risks.
Posing questions makes it sound like we should wait and see; but we should not wait to answer those questions given what we do know. Policy could _always_ be better informed in the future; that does not mean delay is _always_ the best choice.