I only mentioned the question of sex as you brought up the issue of sexual harassment and I don't quite get what you meant by attorneys for ballet, why would an attorney practice slander? Most dancers aren't established, rich enough to hire personal attorneys, indeed why would they and if there's one thing guaranteed to ensure someone never works again in the arts it's to be perceived as a whistle blower or whinger.
You misunderstand. I was discussing the person in power/director hiring an attorney to protect him from allegations of harassment or other misconduct through any means, including blacklisting via spreading false rumors, threats, and financial incentives; we were not discussing the impoverished victim/dancer hiring counsel to slander the person in power. If you are asking why would an attorney practice slander, I would only suggest that people in power and lawyers they hire engage in negotiations. This may lead them to make all sorts of threats and use money to protect themselves or promote their goals, sometimes within the proper boundaries and sometimes overstepping those boundaries.
To answer your question, in certain cases, one may risk a job for principle. For example, people in the arts have lost jobs rather than naming names. Perhaps people do things to protect other, more vulnerable people. Perhaps the issue is intolerable racism, or something similarly venal. Courage and/or beliefs has lead many people to take risks or make sacrifices at times. Maybe other, more clever methods exist to protect people or achieve change, but I can imagine a naive person seeking help from HR or a superior and then being ostracized when the management closes ranks. By the way, complaining about sexual harassment does not make one a whiner. Telling HR that one heard about an alleged rape or abuse of power is not being a whiner or whistleblower. Refusing to protect an alleged rapist over a rape victim is, perhaps, not being a "team player". Maybe the employee thought he was doing the right thing by so doing. Anyway, this is going off-topic, but I wanted to clarify because I thought your response both misinterpreted what I said and drew a conclusion that ignored many factors.
There have been cases when dancers are blacklisted universally but that's more to do with their behaviour than far reaching power of a single individual blighting them wherever they go.
As you said above, one has to have personal, first-hand knowledge; the rest is just based on rumor. I don't know how one would quantify this or perform a statistical analysis. I just thought that in the case you initially raised, it does not make sense that one would remain in a dead end, miserable situation if options were available, unless other factors favored remaining for other reasons. That led me to believe that other options were not available, or he had personal, family reasons to remain in a given city. Options could disappear because of significant, vicious, false rumors, even without a single person having direct power over an industry.