Well, over the years, I have known various folks that "checked a box" for affirmative action that were very privileged, but nonetheless members of minority groups. It certainly violates the intent of the law, but not the letter. So, it's one of those morally ambiguous things like taking a tax break that's legal but not consistent with the intent of the law.
And, of course, any law that permits use of the law in a way highly inconsistent with its intention or purpose is, at minimum, a poorly drafted law.
Also, given that his father was Columbia faculty, he was "deceiving" no one. I'm sure the admissions committee was gtfo with that.
Politically, though, it's pretty toxic in multiple ways, as you note.
Then we have the whole fruit of the poisonous tree problem with the information itself. I think denigrating factual information because of its tainted origin (key word here is factual) is something best confined to circumstances like the 4th Amendment. It seems rare that truth should yield to circumstance or procedure.