Answered by Sayyidi Habib Umar bin Hafiz (may Allah protect him and benefit us by him)
How do we give advice to relatives or friends who follow the Shia branch of Islam?
If you see that they are ready to listen you should try to explain to them in the most appropriate way that the Qur’an praises the Companions, the Prophet ﷺ praised them and so too did Sayyiduna Ali and his children and grandchildren. The example we should follow is the example of the Prophet and the elect of the Prophetic Household (Ahl al-Bayt). They loved the foremost, the first of the Emigrants and the Helpers and none of them spoke badly about any of the Companions. If we do not follow their example, who are we following in reality? Should we follow the path of those who wronged the members of the Prophet Household and cursed them or should we follow the path of the Prophetic Household? Can we express our love for the Prophetic Household by going against their way and following the way of those who showed enmity to them?
Tell them that the chain of transmission of all the four Sunni schools goes back to Imam Ja`far al-Sadiq: Imam Abu Hanifah and Imam Malik received knowledge from Imam Ja`far directly; Imam al-Shafi`i received knowledge from Imam Ja`far through Imam Malik, and Imam Ahmad received knowledge from Imam Ja`far through Imam Shafi`i and Imam Malik. You should praise the four schools without denigrating any of the other schools.