When senior management tolerate misconduct

Hello all, I'm looking for some opinions and advice about a situation at my previous workplace. Essentially, an employee was behaving terribly, and senior management was letting him get away with it. I was disgusted with his behaviour and ashamed to be part of an organisation that tolerated that behaviour. Were my only options to accept it or leave the company, or is there an effective or professional way to protest?

What happened was an employee had sexually harassed, stalked, and assaulted a junior female employee. When she reported it to management and explained what had happened through the grievance procedure, the management found out exactly what was going on and their response was to attempt to do as little about it as possible which I find disgraceful. The management told the junior female employee that the senior employee was important to the company and difficult to replace. They gave him a verbal warning and allowed him to work remotely for 4 weeks so the two would not need to be in the same office for a period of time. The company operates a hybrid policy where people are officially expected to be in the office 2 days a week. So, for his misconduct, he was essentially rewarded with a chance to remotely work somewhere he wanted to be on holiday, which is exactly what he did. The extended remote working was actually subsequently rolled out as a benefit for other employees.

There were some complications. The two knew each other before joining the company and were friends up until this point and the assault and stalking happened outside the office. Therefore, the company chose to declare anything that happened outside the office to be outside of their jurisdiction and a personal matter and legally it is somewhat murky. I generally agree that companies should not be involved in the private lives of employees and that is it very difficult to resolve conflicts between employees, but I believe that the company should intervene when an employee commits a crime against another employee and the victim needs to work in the same room as someone who has assaulted and stalked her. In addition, the junior female employee had just moved to the country as a graduate and was on a visa, so her position in both the country and the company were very precarious and it was very difficult for her to defend herself from a friend/colleague turned stalker even through the police.

Ultimately, it was an ugly situation, and I am deeply unimpressed with how the company handled it to the extent that I have lost all respect for management. I am particularly disturbed by the stalking because it is such a cowardly and pathetic way to intimidate somebody, and the young woman was afraid to go outside for weeks and would have panic attacks whenever she saw him. Sadly, legal protection against stalkers is weak in the UK. In addition, I am disgusted to be part of an organisation that not only has a stalker that I had to see daily in the office but tolerate his crimes and decided to take his side. In a private conversation, the CEO tried to convince me that this employee hadn't really done anything that bad and that it was actually the victim's fault that he had assaulted and stalked her. I was also rapidly losing respect for my colleagues who knew about this and tolerated it. While I don't expect them to endanger their paycheck, I was not impressed that they continued to go for lunch and to the pub with this stalker.

I was never directly involved in this situation, and only learned of the details over the course of several months after the incident from the very frustrated victim. So, I don't have perfect visibility on the full picture, but I believe I have the key points and have personally observed plenty of unimpressive behaviour. Coincidentally several months later, an excellent opportunity arose, and I successfully applied for a position elsewhere. Prior to this incident, this company had been by far my favourite place to work but now I was glad to leave so I would not have to see a stalker in the office each day and be part of an organisation that tolerated him. So, it is all in the past, but I am still conflicted because I still would not know what to do if that kind of situation arose again. On one hand, I want to avoid burning good will and bridges over a situation in which I have basically no power to change. On the other hand, I cannot justify to myself staying silent on a matter which I strongly believe is wrong and this was eating away at me. I made my complaint to my manager and was referred to senior management, where it obviously fell upon deaf ears as they are the ones at fault in the first place.
I'm interested in other opinions on this. Would you be able to work with a stalker who sat two desks away? If I see unethical behaviour and special treatment from senior management, are my only options to stay silent or walk away? The reason I am unhappy with staying silent on this matter is that outwardly, it looks like I am tolerating this bad behaviour which is exactly what I object to in the first place. Is there a way I can protest unethical behaviour from senior management which would be effective or professional in any way?