Although with your example in particular it's probably justified by starting off with very confused beliefs on the subjects and noticing the mess they were in, at least as far as suggesting it to other people I don't understand how or why you'd want to go change a sense of self like that. If identity is even a meaningful thing to talk about, then there's a true answer to the question of "which beings can accurately be labelled "me"?", and having the wrong belief about the answer to that question can mean you step on a transporter pad and are obliterated. If I believe that transporters are murder-and-clone machines, then I also believe that self-modifying to believe otherwise is suicidal.