It should not be possible to use a defence of public interest against a crime. While claims of public interest may be used to abrogate or lessen a *sentence*, the alleged crime should still be investigated and, if there is sufficient evidence, prosecuted.
Therefore I believe that, if there is evidence that the BBC contravened the CMA, they *should* be prosecuted. It will then be up to judge and jury to decide if they are, in fact, guilty. This will set a precedent for future cases and act as a guideline for other journalists considering similar acts.
I actually believe the BBC had some justification in this act, but if it is not tested in a court I am concerned that it will weaken the protection afforded by the CMA, effectively making it legal to be a bot-herder and sell / hire your botnet to others.
The alternative is for the CMA itself to be amended by Parliament to clarify / close this 'loophole'. IMHO, given the Government's track record on IT legislation and their proclivity for sneaking in authoritarian clauses, we *really* don't want that.