I don't think you've characterized it correctly. In this day and age I'm not sure anyone really cares about chastity or not, per se. 
My understanding of the identity protection is that it is to provide privacy to people who may be the victims of a deeply personal assault, which they may feel ashamed or humiliated about. The functional effect is to encourage complainants to come forward, which I'm sure most folks would completely agree with. 
I don't  buy your assumption that in the "overwhelming majority" of sexual assault acquittals the attacker escaped justice. I understand the urge to say this but the reality is that you have zero data to support this, it is pure supposition and can only be based on a bias towards complainants. Both parties will of course maintain their position regardless of the verdict.  As a society and in terms of public policy, the only truth we can ever be sure of is what the court decides.