I think the "doing so" he said refers to the considering of our body parts as swappable, not the act of swapping them. By not feeling like they're important integral parts of our identity, we may be careless with their health.
That concern is reasonable because it is difficult to swap parts, so we should keep them in working order rather than relying on the remote possibility of replacing them. But conversely that means if it were cheap and easy to replace them there wouldn't be as much need to take care of them.
Integral part vs. disposable is not a binary distinction.
