I wonder, Elliemay, if the solution lies in encouraging T's not to give a simple "yes or no" answer to a question that, except for extreme cases, doesn't lend itself to a simple answer due to its complexity. Perhaps it's a question that requires more of a discussion about the human inability to guarantee 100% safety due to some of the reasons that were discussed in the other thread, and about the fact that abuse and its effects exist on a continuum that in many cases makes it impossible to draw a clear distinction between survivors and abusers.
We all tend to feel more comfortable with simple "yes or no" answers but since a healthy response to life circumstances requires the ability to recognize and deal with gray areas, and good therapy requires us to think abstractly and in depth, maybe this is a question that T's should be better prepared to answer themselves. That way they can discuss it in more detail when a patient asks.