Whilst discussions of ISO tags and rotor-machines are kinda kiddie fun, they all seem to ignore the power and human impact on decent society of strong cryptography. We all know that the principle and foremost purpose of cryptography is to facilitate the destruction of the enemy. You can decide who/what is the enemy, which is in itself a morally challenging question. But not all of that is moral :-( So should we question this with an appropriate tag, or rather delete/down vote posts under the guise of ‘conspiracy’? Abstract: #cryptography_without_morality?
I don't think we should have an ethics tag. This site is only about cryptography, its use, the theory behind it, and how to attack it. I also have to disagree with this claim:
the principle and foremost purpose of cryptography is to facilitate the destruction of the enemy
I'm not sure where you're getting this idea. Perhaps this was the case early on when cryptography was a tool exclusively used by the military, but that's not the case today.
For questions related to the ethics of secrecy (or any other properties cryptography can provide, such as integrity, proof-of-work, or non-repudiation), it would be better to ask on Philosophy or Politics. Furthermore, I'm not aware of any open questions which are philosophical in nature that would get that tag if we even had it. Are there any questions in particular that you are thinking of?