it is not just permissible but can also become obligatory for one to do this in order for people to know the truth and be guided.
Fatima Al-Zahra (sa) in her Fadak sermon instructs is to fight the heads of kufr (such as the khulafah who usurped the position of Imam Ali). This 'fight' can be an intellectual type of war or fight to establish truth,
Yes, if one isn't in a state of taqiya or danger then they may expose these figures in an academic manner by using the sources of the opposing sect. One doesn't need to insult for them to be able to achieve this although some may become naturally offended by hearing mere criticism towards figures they regard in high esteem.
May Allah grant you success