They do create antimatter in CERN.. they also managed to contain it for record times. Its just that the quantities they make arent dangerous. Its literally generated with only a few subatomic partilces at a time. Not enough to do any harm.

There have also been worries about blackholes, but the same thing applies there.. if any such black holes even can be created at the LHC, they'd be so incredibly tiny that they would evaporate before they could do harm. 

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