In a vacuum, appealing to authority is fallacious. An idea must stand up on its own merits.
IRL, things get fuzzy. No one has the expertise and time to derive everything from first principles and redo every experiment ever performed. Thus we sadly have to have some level of trust in people.
To be fair, the name Antifa is used pretty much exclusively by radical anti-authoritarian left groups.
The libs don't organise into black blocs to beat up fascists, they write to their congressman to ask for stricter hate speech laws.
The tankies, despite creating the first group to call itself AFA, don't participate in them much in the modern day because they try to subordinate such things to their party, which goes against the decentralized ethos of what most people call Antifa.
This leaves anarchists, libcoms, and a small smattering of demsocs and Trots. Thus it is completely fair to refer to "Antifa" as a left-wing phenomenon.
A friend and I were recently discussing how spineless modern boycotts are.
We set a goddamn deadline for when the Reddit boycott ended. No wonder Spez just waited. Most people then just continued using the website. What a disgrace.
Imagine if after one week of the genocide in Gaza, the BDS efforts just stopped. A boycott must be indefinite. It should go on until demands are met.
We do this in Ireland