What is the ruling of the Ulema of Ahlus-sunnah wal Jama' with regards to the shia and WHY?

Salam .Ulamas said that the shia is a misled muslims because they do not recognize Abu Bakar,Umar Bin Khattab and Ustman Bin Affan as Khalifahs or leaders of muslim community. They have the opinion that the first khalifah after Muhammad pbuh ped away is Ali As.They are non muslims just like Ahmediyyah followers