Anonymous is talking about non-inclusionary zoning. In most places in the US it is not possible to build any more than one single family house on a 1/3, 1/4, or even 1 acre lot. This is required low density. With a few exceptions (Portland area, for example), you can always spread out and buy as much land as you want pending your own personal finances, but in suburban US for most our history as a nation, high density housing is a bad word and it has been effectively regulated out of existence.
There is a mentality that this hurts property values and higher density means bringing poverty and undesireables in. Nothing to do with psyche.

Found at your Wikipedia link:

A detailed analysis [18] concluded that the RHIC collisions were comparable to ones which naturally occur as cosmic rays traverse the solar system, so we would already have seen such a disaster if it were possible. RHIC has been operating since 2000 without incident.

Phew! I was worried that I overslept and missed the Strangelet singularity! Talk about stating the obvious.

Wikipedia: -1 Redundant