From Longman Dictionary of Contemporary Englishbe cruel to be kindbe cruel to be kindHELPto do something to someone that will make them upset or unhappy in order to help them in another way → cruel
Examples from the Corpus
be cruel to be kind• George did not like being firm with Lennie but he knew that he had to be cruel to be kind.• So now I've got to be cruel to be kind.• You have to be cruel to be kind.• You've got to be cruel to be kind, and dismantling the Dome would be the best solution for everybody. 