Guard against this possibility is remarkably easy: Nobody hits on job applicants. If you are interviewing people, it is your duty to know this, and your company’s duty to ensure that you know this.
Either that, or you had better have one hell of a documented paper trail explaining how they were good enough to interview, but not good enough to hire, and explaining why the person you ended up hiring was clearly superior.
In my experience, any company with the kind of process that can defend itself against such lawsuits wouldn’t permit an employee to expose them to the lawsuit in the first place.
If one of their managers has read this, I’m sure they’re horrified.