I think a "no offender" policy creates a false sense of safety and security for SA survivors, simply because T's would have to be mind readers to know what kinds of issues a new or current patient might bring to therapy. The fact that a patient hasn't identified himself/herself as an offender does not mean he or she isn't an offender, and realistically, unless it's court-ordered treatment, who would reveal that to a T prior to establishing trust within the relationship? So basically, short of hanging a "no offenders" sign on the door, I don't see how a T can be certain that he or she is not treating an offender. And even that couldn't guarantee that an offender wouldn't come in for treatment of other problems. Since most offenders don't see their behavior as wrong, and their thinking is very distorted, it's entirely possible for an offender to enter treatment for a variety of other reasons, and because he doesn't see himself as an offender, a "no offender" policy would not necessarily mean anything or apply to him.
I think that policy also creates a false dichotomy, lending itself to black or white thinking in both the T's and their patients because it separates survivors and offenders into two separate and distinct categories with no overlap, which does not represent reality. It creates an "us vs. them" illusion that does not exist in the real world. Some people are survivors. Some people are offenders. And some people are both. Attempting to protect and remain loyal to the treatment of SA survivors is a noble gesture, but not particularly realistic.