I vote "All of the Above" is unethical, assuming we're referring to selling or trading the card to someone else without disclosure of the alteration (or "restoration," "improvement," "cleaning," "wiping," "sprucing," or whatever phrase you like).
As for the PSA question, someone suggested in the previous thread that the card is whatever the PSA label says it is. I strongly disagree, and I'll use Fritsch W512 prints as an example. Because PSA dabbles in incompetence, it has slabbed a number of obvious Fritsch prints as original W512 strip cards.
Getting a lazy PSA grader to put "1926 W512" on the label doesn't magically transform an ersatz Ruth into an original one. Let's say I knowingly submitted the above Fritsch print to PSA, and PSA slabbed it as a W512 Grade 1. If I sold it to someone without disclosing that it's really a Fritsch print, then I committed fraud.
Bless your shriveled black heart if you're willing to give me a pass in that scenario, but the reality is that you're a scumbag enabling another scumbag.