Is it true that the Shia believe that all the non-Shia are Kafir because they reject the 12 Imams and have love for the people who oppressed the Ahlulbayt AS?
It is untrue. It is one of the many false accusations against us fabricated by our enemies.
We believe that followers of any Muslim sect being Sunni (Hanafi, Shafi'ee, Maliki, Hanbali, Barelwi, Deobandi or Zaidi or Abaadhi or Ash'ari or Salafi or Wahabi etc are Muslims like us.
Even those who claim that we Shia are Kafirs are misguided Muslims and we never consider them as Kafirs.
Wassalam.