never had a CBS,but I wanted one. and after research, I read that they can get really aggressive, even kill small fish and other shrimp. I decided not to get it.
But to answer your question, I think it's definitely a possibility that the CBS may eat your peppermint. Pepp's aren't the most expensive shrimp, so it's up to whether or not you want to risk the pepp's life.
A lot of ppl have CBS though with absolutley no problem.