In my view, if someone invades your territory and starts attacking you, you have no obligation to follow any sort of "principles" or "rules" when it comes to how you fight back. Anything you need to do to the attackers in order to defend yourself and your people is, by definition, morally defensible.
(Do note that I said "need". Doing arbitrary messed-up things that don't actually further the goal of driving back the attackers is not ok.)
US exceptionalism is a prominent feature of every republican and democratic president since decades.
It's sad, because if US did, and led by example, it could've pulled serious weight internationally on plenty of matters.
Instead it can only do so by economic or military leverage, which, at the end of the day is not enough of a leverage to avoid confrontation.
Iran's use of cluster munitions to attack swaths of Israeli cities is also against the Geneva Convention (though I'd again point out that we started hitting civilian targets in Iran first).
Both sides have violated the conventions, but the US and Israel have violated them to a much greater degree (especially Israel and all their attacks on Lebanese civilians not to mention razing Gaza).
We have to wait and see if Iran is fighting a woke war.
The point is there are a great deal of people, even in the US, who advocate that it is unreasonable to hold people fighting the west in general and US in particular to the Geneva conventions. I don't know where this idea comes from, because morally it is of course indefensible, but there you go.
I would expect the number to be bigger in Iran. I would expect the number among IRGC extremists to be even higher than in Iran in general.
Second: war crimes have 2 interpretations. First as violations of the Rome treaty which require that the state where the warcrimes happen has signed the Rome treaty. Iran hasn't.
The second interpretation of warcrimes is that they are violations of the Geneva conventions, and the reaction would be that the UN security council intervenes. Well, the UNSC has preemptively declared they will not hold Iran to account for warcrimes (to be exact: France, Russia and China have declared they will veto). So at minimum you can say that Iranian warcrimes will not have any "official" consequences.
The world and the UN have decided that warcrimes "don't count". As in there will not be any consequences unless the government of the country where they happened implements those consequences.
Third: Iran has already kidnapped a US civilian (a reporter, Shelly Kittleson) and are holding her hostage. This is already a violation of the Geneva convention. They have also kidnapped hundreds of foreign nationals of other nations and are also holding them for ransom, which is also a violation of human rights, ie. a warcrime.
So those are my three reasons Iran won't hold itself to human rights standards.
Also, I dont see UN punishing Israel or American war crimes either ... so it makes sense to not apply "whatever goes" standard to aggressors and different one to the defender.
Expect there to be a lot of operatives of the US in Iran. Not to sound like a conspiracy theorist, but it wouldn't be the first time a CIA or something operative is caught and this is the cover.
In war the first victim is always the truth
I think I'll need some reeducation on this concept of "dignity" you speak. Could you explain further?