Leaving aside Boris Johnson and the distastefulness of his language, there seem to be two possible situations when it comes to alleged child abuse: good enough evidence to bring a prosecution in court, or not good enough evidence to bring one. An alleged child abuser can be either alive or dead. Where there is good enough evidence, I suggest that an abuser should be prosecuted if alive and exposed if dead (as in the cases of Jimmy Savile and Michael Jackson). The fact that a dead person cannot defend themselves is then less important than the benefit to their victims from having what happened to them acknowledged and condemned, and possibly to the public from deterring other potential child abusers.
Where there is not good enough evidence, surely allegations should not be made public whether the alleged abuser is alive (like Cliff Richard) or dead (like Leon Brittan or Bishop George Bell). The distress caused either to them or to those who care about them is not justified.
However, the question of whether there is good enough evidence is usually answered by a police investigation – unless the alleged abuser is famous enough that somebody will make a documentary about that evidence, as with Michael Jackson. So the question then is, given that the police do not have infinite money, how much public money to allocate to investigations of historic crimes (where the alleged perpetrator is still alive – I don’t think police will investigate otherwise) and how much to allocate to investigations of present-day crimes.
There is probably a case for the investigation of present-day crimes having higher priority, as successfully prosecuting a present-day criminal will a) prevent them from committing crimes for a time (while they are imprisoned) and possibly deter them from committing future crimes, as well as b) deterring others from committing the same crime. Whereas successfully prosecuting criminals who have not committed the crime for a long while will have the second good effect but not the first. Both types of prosecution will benefit the victims.
Therefore it is probably better to allocate a smaller proportion of the available money available for investigating crimes to investigating historic crimes.
I wonder what the reason is for having a statute of limitation is on some crimes – that is, an alleged perpetrator cannot be prosecuted for them after a certain period of time.