There are few cases where it seems appropriate that a man of 84 should be sent to prison, but the five years and nine months to which Rolf Harris has been sentenced seem, if anything, lenient. He may well serve the rest of his life in jail, but in terms of mental illness and vulnerability, the damage he did to some of his victims has for them amounted to a life sentence. The judge, Mr Justice Sweeney, was clear that he believed Harris's abuse of his daughter's friend that began when she was only 13 had undoubtedly caused her to become an alcoholic. What Harris did – and kept on doing for decades – was traumatic for all his victims. If any good can come of this, it is that their courage in coming forward and giving evidence should give others the confidence too.

But Harris is a particularly repugnant case and it has understandably provoked a particularly high level of revulsion. There has been something uniquely offensive about the hypocrisy of his avuncular public persona, which suggested to children that there were friendly adults out there, who were on their side, and who could be trusted. He even made a song to teach them that they controlled their own bodies. This false and deceitful intimacy, which has so shocked his millions of fans, was even worse for his victims, some of whom were close to his family in real life. Their horror and the depths of his betrayal of their trust are difficult to imagine.

Part of the widespread revulsion and condemnation of Harris may be a delayed reaction to the enormity of Jimmy Savile's crimes that went unpunished despite the cries for help from some of his victims. Perhaps Harris and other Yewtree figures are being cast out of society with such vehemence because that could not be done to Savile while he was alive.

The complexity of the sentencing of the 12 separate offences of which Harris was convicted is a reminder of how the climate has changed. When he began his long career of abuse, the maximum sentence for indecent assault was just two years. Under today's rules, he could get a life sentence for some of his crimes. For too long women were expected to put up with sexual abuse as the price of their gender. But if his crimes might have looked less extraordinary when judged against the exploitative and abusive celebrity conduct of that period, the damage they did was as profoundly harmful then as it would be now.

Still, the Harris trial was not only about the righting of personal wrongs. It was at the same time part of a great shift in public morality. Like the other trials arising from Operation Yewtree, and in the aftermath of the Savile scandal, the Harris trial was at the same time a real and a dramatic performance. These trials are significant not only for the justice they do, but also for the justice they show, and for the better justice that they point towards in the future. Big trials on morally significant issues are effective public rituals – real actions that also carry a clear symbolic meaning that changes and purges society.

Times change and morals with them. There has been a great revolution over the past 50 years that has improved society immeasurably. It is not yet complete. Too many victims of abuse are reluctant to come forward for fear of being disbelieved. Stereotypical ideas of victimhood sometimes diminish the seriousness with which complaints are treated and make convictions harder to obtain. Some of the condemnation is sometimes theatrical. Some of it comes from people not normally given to moral reflection. And some of it comes from people who may have done some of the same things themselves if they had had Harris's opportunities at the time he had them.

All these things are changing. They need to change more. The revolution has been slow and messy and sometimes very painful. The Harris trial will not be the end of it. But it is a significant and worthwhile milestone all the same.