What is the ruling on accompanying people of differing madhhabs after inviting them to the madhhab of Ahl al-Sunnah wa al-Jama'ah, without a positive response?

You must advise your companion to avoid associating with people of innovation (Ahl al-Bid'ah), especially the Rafidi Shi'ites, because of the danger this poses to his faith and worldly life. For the Rafidi casts doubts that make a Muslim question his religion and harbors enmity towards the people of Sunnah. Prophetic traditions have urged choosing companions wisely, such as: "Do not associate except with a believer, and let no one eat your food except a pious person," and "A man is upon the religion of his intimate friend, so let one of you look at whom he befriends." The Salaf warned against associating with people of innovation. Abu Yusuf said: "It is not befitting for anyone among Ahl al-Sunnah wa al-Jama'ah to mix with any of the people of desires (Ahl al-Ahwa') to the extent of befriending them and making them his close companions, for fear that they might lead him astray or lead others astray through his companionship with them." Imam Ahmad said: "If you see a man from Ahl al-Sunnah with a man from Ahl al-Bid'ah, advise him. If he does not abandon his companionship, then affiliate him with him."