I recall reading of a Jewish prohibition against studying or developing the art of persuasion or rhetoric, because it distracts from the content and may be used to manipulate others. Could you please confirm this and perhaps share a reference?
AskTheRabbi.org answered:
It is only prohibited to persuade someone to do something that is forbidden. There is no direct prohibition for being an expert rhetorician but there may be a secondary issue of what is called "Geneivat Da'at" which is fooling someone into thinking something other than the truth.