A dirty trick is still a dirty trick. Maybe the paper deserves some credit for half confessing it. But what choice did they have? They aren't a megapower like CBS. And the email was already out convicting them of misbehavior.
Yes, they were wrong to withhold the fact that the question was planted. And now they are wrong not confess that planting a question in such circumstances is just plain wrong.
The reporter was stupid to have left a paper trail with his email boasting about his own cleverness. But stupidity doesn't excuse professional misbehavior. Now he should be disciplined or fired.
That probably explains why the newspaper is making no bones about apologizing for what happened, it wasn't malicious intent on their part as it would be in the case of the NY Times or CBS, but a case of them being taken advantage of by one of there reporters.