There are risks to making too many rules about who gets to be a member in your club.
And no risks in being too open about who gets to be a member of your club?
Just for clarity, when I was talking about how users are emotional about the front page and react intensely when they see something they don't think belongs there, it was in the context of an experiment we'd run to randomly place stories from /newest on the front page. Users reacted disastrously, not so much because of scope but because the median article's quality is just really low. That's true about in-scope topics like programming as well as other topics. I hope that makes sense.
As for 'who gets to be a member' - we don't restrict that nor want to restrict that. Everyone with intellectual curiosity, i.e. everyone, is welcome. The only requirement is actually using the site in that spirit. This is not so easy, of course, especially when the more activating topics show up.
For instance I've worked for companies (at least two) where, the set of goals for the hiring process, and what was actually practiced, were pointing in somewhat different directions. In the end it really came down to "how like us is the candidate". All while sailing under a "diversity is good" flag, being convinced that we lived our values, and (in one case) increasingly experiencing the problems stemming from a hardening monoculture. What happens when you try to resolve that situation is, to put it carefully, "interesting".