Actually - it is one rule for all, and that is the rule of law.
I knew before I even opened the link that the reason the CPS would give is 'the unrealistic prospect of a conviction' which is the usual reason the CPS gives for dropping prosecutions.
If you read the link, it is clear that their decision is a correct one, there is nothing to be gained either in terms of value for money for the tax payer, or the maintenance of the credibility of the CPS, in bringing a trial that is not likely to result in a guilty verdict.
The people involved can deal with what they know to be true, the CPS can only deal with what it can prove to be true, and often, as in this case, the two are not the same thing.
To drop my objective opinion, and offer my personal view - it is appalling for the victims that this man can escape due sanction for his behaviour, but the legal system has to operate fairly for everyone, or it becomes meaningless.