I am astonished to find that Amit Varma has a less cynical view of government than I have, at least going by this post.
See, the thing is, in a corrupt Indian government organization (pardon my redundancy) there are no half measures. It is not like only Jothikumaran was corrupt. Usually, the entire organization, right from the chaprasi level to the very top, has a stake in the corruption. It is usually an open secret as to how much one has to pay whom for what. So, it is not like the organizers of the sting operation would have any reason to doubt whether Jothikumaran was corrupt or not. It would be just a case of finding the evidence. Of course, there are many ethical issues in investigative journalism and there are more when sting operations are involved, but the possibility that the person being stung is actually honest ought not to be one of them.