The Muslim, Sunni, is just, he is moderate by nature and rejects all forms of extremism.
One of the Usūl and principles the scholars mention is:
أن العبرة في الحكم على الأشياء بالمسميات لا بالأسماء
‘The criterion for judging matters is based on their reality and not on what they are called.’
So whereas every Sunni is judged as a Muslim and non-Mubtadi’ (until proven otherwise) and every Shi’ī as a Mubtadi’, yet the opposite can be true i.e. the Dhāhir is just an indicator that can be proven wrong with the actual reality of a thing or someone’s (beliefs).
Having said that:
The one who calls himself Shi’ī, including a Twelver who doesn’t hold Kufrī beliefs and doesn’t pray to Imāms (although extremely rare) = Muslim brother in faith, however, Mubtadi’.
The ‘Sunnī’ who prays like Pīr Baba X, Y, Z and hold other Kufrī and Shirkī beliefs = Pagan Mushrik.
It’s not about Sunni or Shia and name calling, it’s about the reality of matters, it’s about Tawhīd and Shirk. So don’t be fooled by labels.