Question: When does a man exit the bounds of Ahlul Sunnah?
Answer: If most of his actions are in opposition to the Sunnah. For example: he establishes mawlids [the birthdays of the Prophet] and he calls upon other than Allah and that is an innovation that removes someone from the religion. Supplication to other than Allah is an innovation that removes someone from the religion. He curses the Companions. The one who curses Abu Bakr and Umar is a filthy Raafidi, not from Ahlul Sunnah.
If it occurs from him one innovation, or two, or three and he is a Sunni, I hope it [the innovation] is overwhelmed by what is with him of virtue. And in Allah is refuge sought
What is important, oh brothers, is he exits from the bounds of Ahlul Sunnah if he opposes a foundation from the foundations of Ahlul Sunnah. In Allah is refuge sought.
[Taken from here: https://muqbel.net/fatwa.php?fatwa_id=2335 ]
Faisal ibn Abdul Qaadir ibn Hassan