Joseph: Thanks for the clarification.
So the mechitza defends against that specific type of active evil inclination “that which is present when men and women converge together in a party atmosphere” (Joseph).
However the mechitza does not eliminate the other types of evil inclinations that may be present for other reasons, etc. Thank you. I was wondering how a mechitza could cure every yetzar hara (because I seriously would mechitza my whole house if it worked). Clearly that was not what you meant.
Thanks again 🙂