There are nearly as many non-parent commentators feeling unjustly maligned in that thread as there are parents feeling the exact same thing
It's the polarization of choice. Because there are options available, everyone feels as though his or her choice is being criticized by everyone else all the time.
Most adults in the US can avoid kids if they want to. That wasn't true fifty years ago. Up until about 150 years ago, the demographics of humanity was skewed heavily to the 18-and-under crowd. Few adults lived to 50, let alone 80. High infant/child mortality and poor birth control meant a whole lot of children. Getting away from them was inconceivable. No one complained about kids in the workplace, except some do-gooders who wanted the kids to go to school. The only problem with kids in bars was when they wouldn't give you a seat.
Most of the world is still like this.
If someone can make money guaranteeing residents a community free of children, why shouldn't they?[...]What's the negative impact on society if this occurs?
Well, segregation is bad thing for society. The more isolated groups become, the less likely they are to a)accept one another b)treat one another well c)avoid abusing one another. If there are no kids in your community, or very few, it is unlikely that your community will consider them worthwhile members of society. You won't pay for schools for them, or medical care, or day care, or public transportation, or playgrounds, or anything else which is solely or mostly for them. This is bad, because most kids can't afford these things on their allowances and occasional tooth fairy bonus.
If there are no, or few, kids in your community, you will be deeply offended when they are brought to any of your public spaces, spaces which you have become used to thinking of as "for adults". You will be indignant at the imposition of children into public life, and you will resent any efforts to accommodate them. You will be annoyed at their sandcastles cluttering up your beaches, at their strollers blocking your sidewalks, at their fabulous parking spaces right up by the grocery store door when they can't even drive.
If there are no, or few, kids in your community, you will find the behavior of individuals strange and extreme, and you will be more likely to stereotype all on the basis of your very limited (and only noted where negative) experience. You will find their presence in groups of three or more to be threatening and hostile, you will find their high-pitched voices grating, their lack of height annoying.
All of these are attitudes have shown up in the comments of these two threads. There is a tremendous amount of justification and defensiveness on the part of childed and childless adults, both of whom feel attacked by the other. Because that's how humans tend to see the Other; as both crazy and hostile.
That family care is primarily a feminine responsibility in this society, and that women may be criticized by strangers for everything they do, wear, and think, only adds to the perceived hatin'.
Even as more people consider it inappropriate to discriminate on more subjects (to the old standbys of race and religion we've added sexual orientation, health/disability, looks, and weight), pretty much everyone seems to think that age discrimination is just fine. Either adults who don't want to be bothered with children in their spaces, or adults who have very clear opinions on what is acceptable for the children, and expect all of society to accommodate the prescribed needs of kids. It's either a two-year-old at an R movie, or an R-movie bowdlerized down to G.
Here's what it comes down to: My kids are perfect, and if you disapprove of their behavior, it's because you're bigoted against kids. I go out of my way to ensure that they are never disruptive or disturbing in any way in public, such that mostly I just keep them doped up and out, because I live in terror of anyone being in any way put out by them. The Spouse, though, he can take them out and do whatever, and he just gets heaped with praise. Of course, he's kind of big, and potentially scary, so no one would dream of ragging on him.
Everybody else's kids suck though, and it's okay to rag on them. Except the offspring of any of my friends and relations, all of whom are very nearly as perfect as my own kids.