It kind of depends on what you think possession is. I think of it as a metaphor for mental illness, most likely an illness that caused rather strange behavior where a person seems to have more than one personality. This multiple personality disorder, schizophrenia, or bipolar disorder.
Any persons suffering such, might be unhappy to see the priest, especially if they had been getting hassled for supposedly having the devil in them. However, once again, whereas physical escape may be impossible, mental escape still is possible.
Now, if the author or screenwriter did believe in devils and possession, I suppose it changes things somewhat. Mostly it means that the author is delusional or is writing as if delusional, and therefore it becomes somewhat difficult to interpret.
But if the devil is that which society disapproves, and that-which-soicety-disapproves goes and plays the piano, it is still an effort to escape.
It’s only not that, I think, if you believe in a literal devil living inside people. If that’s your reality, then I can’t help you. I don’t mean you, Mr_M, but you plural—people who think the devil is a real entity, separate from humans.