that is very odd actually... peppermint shrimp don't usually harm sessile invertebrates... but they CAN occasionally do odd things.... i mean it happens with all our aquarium stuff, they have minds of their own (I once saw a yellow tang that destroyed an entire shipment of cleaner shrimp....)
you might try moving the condy... see if that helps... are they actually tearing it apart or had you just fed and they were tearing food away from it?
how is the condy doing? is he good and healthy?