Hard to say actually as the tang in the background looks like it is actually a pretty good size and is too large for the tank(i still think but cant be sure because of the photo). Unless it is a tiny 2-3" sailfin then it absolutely wont be comfortable in this size aquarium, causing unneeded stress to the fish for our own viewing entertainment , which is unethical.
Correct. Without asking any quantifiers, Y'all started lecturing on fish selection in somebody else's tank.
Did you ask about fish current size or future upgrade plans before figure out that OP should be corrected?
I see No issue having a 4" FF and 3.5" sailfin in that dimension tank. They will need an upgrade in the future. Sure.
Unethical, Absolutely not.
They were a bit blunt and didnt directly talk about the actual fish size or if OP has a plan for upgrading it to larger tanks as it gets older, but this is a forum and it is populated with opinions. Even a lot of the "facts" we have are just opinions based on anecdotal evidence and not in truth facts.
Conflating opinion and fact on a forum is indeed prevalent.
As it relates to ethics in this hobby, eagle Steve has a great discussion thread on it. Check it out. Mayor take away for Me from that thread being what I believe to be ethical, means exactly Jack because ethics is a personal standard. What someone else finds until doesn't mean that it is.
There are some ethical questions we all pretty much agree on. There are Way more that we don't as evidenced by the numerous discussions about this, that get locked and buried because people are passionate.
Just as I have no right to force feed you my religion and politics, I also have to right to apply MY ethical standards to your reef, and expect you to care.