What did the Buddha said and taught about sharing demerit?

"It seems not customary to share demerit in certain Buddhist traditions. However, I've recently heard demerit can't really be shared. What did the Buddha say about this?" What's the matter with bringing others to approve, or rejoice, or appreciate ones demerits made by body, speech, thoughts? What's the result for one if joining anothers demerits? And refined: What's the different between demerits and sharing them, for an 'unfettered' heart?