You mean there *never* have been observed any evidence of a micro-singularity in any of these powerful particle-accelerators? How do they know it will decay in a given amount of time for a given mass? How do they know the mass of these things won't "tug" on the walls of the particle accelerator pulling them in...
Do you think in their attempts to see if one might exist that they might try to deliberately create one?
Black holes aren't destructive because of gross gravitational attraction; after all, all the gravitational force they have is the same as that of the mass that went into their making; say, the mass of two colliding protons, just as Tubbythin said above. They are rather more destructive because of their tidal effects, which tend to tear matter apart when it gets close to the event horizon. Tidal effects are dependent upon mass, but also inversely to the cube of distance (if I'm reading the equation in
http://en.wikipedia.org/wiki/Tidal_force correctly). That means that a 2 proton mass black hole will not allow anything to stand in its way, but then solid matter at that dimension is mostly empty space anyway. Consider the typical explanation of that empty space: an atom of, say, iron, expanded to the size of a football stadium, with the electron shell extending (sort-of) out to the nose-bleed seating, the volume of the nucleus would be represented by a baseball on the 50 yard line. Mostly empty.
That is not the same things as saying they don't represent a danger. The problem is that if they exist and are in orbit within the earths radius, then they will occasionally rip through and accrete the odd particle or nucleus in their way, and thereby grow. If there is no counter-balancing evaporation, then, eventually, there could be problems, as the tidal forces get larger and extend further.
As an engineer I'm qualified to make that sort of napkin-analysis, but not much more. For detailed analysis I have to trust those that have more detailed knowledge. I am confident that they can be trusted in the main to provide a true answer about this. After all, they and their families will not escape the effects. It's also not like they've forgotten about the possibility; the controversy has seen to that, if it were a possibility. There are any number of science fiction stories based on this idea; I think in particular of James P. Hogan's "Thrice Upon a Time".
Before the first atomic blast, Oppenheimer and other scientists speculated that the extreme conditions inside the blast might ignite all matter, with some unfortunate consequences. This became less likely as their knowledge increased, right up until the blast. (See Richard Rhodes, "The Making of the Atomic Bomb")
Therefore, this sort of question asking is not in error or in any way out of place. It is, in fact, vital. But, you and I don't have the raw expertise to decide. Foolhardy? Perhaps, but during the cold war we lived with the possibility that one balmy person could end it all, and we elected paranoids like Nixon to see to it; and their side sported Brezhnev and Andropov. Now,
that was taking a chance. No
about it.
