Well firstly, the last line of that Mirror quote, while not actually incorrect, is somewhat misleading:
"Police decide whether or not to name an arrested person based on a balance of the suspect's right to privacy and the public's right to know"
And it's misleading because in the overwhelming majority of cases, that balance is firmly weighted towards the suspect's right to privacy. In fact, it's far more than the suspect's right to privacy: it's the suspect's right to be spared public opprobrium and finger pointing before (s)he has actually ever been charged with any offence.
In the specific case under discussion here, I can't think of any reason (based on the apparent basic elements of the case) why the balance would not likewise be firmly tilted in favour of preserving this man's anonymity at this stage. The police have identified an alleged victim, and the alleged perpetrator appears to be cooperating with their investigation. Even if police are concerned as to whether there may be further potential victims of this man, the correct time to appeal to them would be after any charges are brought in respect of this current case (but before that case goes to trial, so that any potential further crimes could be tried concurrently).
Concerning the main topic of that Mirror article, I think it's important to remember the principle of proportionality. If, say, an office worker was arrested on suspicion of a serious crime, then that person's company would be entitled to know this, and they'd be entitled to suspend the employee pending either a) the employee being cleared without charge, b) the employee being charged but then acquitted in court, or c) the employee being charged and convicted.
But what the person's company would NOT be entitled to do at the point of that person's arrest would be to (e.g.) post notices on every floor of the company's offices informing everyone that (e.g.) John Smith had been arrested on suspicion of assault, and to post the same information on the company's website.
