Maybe it starts when some people start to apply some power on other people ? But all your examples are people talking about themselves : their own lives, their own choices, their own specifics, their own struggles. I would say people can have all this and mention it as long as it stays on the fringe and does not become a topic to debate. This would be outside the scope of the group.
Maybe other people should avoid commenting on peoples life / choices / specifics / struggles, and the atmosphere may stay nice.