I think that the worry that people have is that they think that a molecular level black hole (if produced) would sink to the centre of the earth and gradually swallow the earth up, atom by atom.
A reasonable concern. Ray Bradbury wrote a "Golden Age" science fiction story about that happening on Mars, I think.
BUT,
(1)
The particle accelerator doesn't have even a part of a bit of a small portion of a fraction of what is needed, energy-wise.
(2)
Black holes have a life-time related to their mass. With such a tiny mass, any black hole would radiate out of existence in such a short time that the systems might not even notice it. (Black holes are fuzzy and have no hair). The engergy given out would be about the same as the collision put in when creating it.