Just yesterday someone described themselves to me as a non-practicing Buddhist. I cannot say that I have heard this term used before and I found it a rather strange one. Strange because it implied that being Buddhist is an identity apart from practicing and trying to live by the Dhamma. It makes sense to call yourself a non-practicing Jew because Judaism is to a large sense a culture and an ethnicity as much as a religion, so you can have one without the other. I have heard people describe themselves or someone else as a non-practicing or lapsed Catholic. This makes sense too given that Catholicism is so all-embracing that it imparts an identity beyond one’s specific culture, race and so on. But a non-practicing Buddhist?
To me this makes no more sense than it would be to describe oneself as a non-practicing athlete. “I have never competed in any athletics, I do not have an athlete’s build and I have no interest in or knowledge of athletes, so I’m a non-practicing athlete.” An athlete is legitimately and properly called such by his or her doing of athletics. And equally it makes no sense to describe oneself as a non-practicing Buddhist. You either practice or genuinely try to practice the Dhamma and accept its main philosophical propositions or you do not. If you do you are a Buddhist, and if you do not you are not. You can be a former Buddhist, you can be a bad Buddhist (a far from endangered species) but you cannot be a non-practicing Buddhist.