I feel urge to act badly

My ex told his family member something untrue and now that person is not speaking to me. I have the urge to make the statement true by doing what my ex told the family member I did, yet I’m thinking I would be acting badly.
I think of that idea of expectations – if you are going to act as if I did this, I might as well do it.
I think about responding to this urge periodically and have not given in to it, but sometimes think I should.