Jotaf, your concerns are specifically addressed in the recent LHC report.
In reverse order,
3) Bubbles of vacuum decay expanding at the speed of light are a problem in any reference frame, so they are well constrained by astronomical observations. Most cosmic rays are coming inwards, so many of the particles would have to escape through the planet, neutron star, etc. Anything with an electric or magnetic charge would be stopped (magnetic charges come on monopoles). This means everything but neutral black holes can be immediately bounded by
2) The conservative estimates are done with the density of neutron starts, iron at less than a TPa is nothing in comparison.
1) Section 4 gives a series of arguments, each assuming that the expected behavior that prevented disaster in the last argument is mysteriously absent and considering the situation again. Only the first assumed Hawking radiation will occur, the last assumes neutral black holes that never decay and bounds on their growth rate.
To be sure, this report contains no equations, but it reads to me not like condescension, but a summary of the results of people who have done the math.
It seems like the details should be in the references. Try following the citations, e.g. next to the assertion that someone has bounded accretion rates of neutral hawking-free black holes assuming various numbers of small dimensions, or that hotter collisions should be less likely to produce strangelets.