How can someone respond to Sunni Muslims who question why Shia Muslims refer to their Imams as AS instead of RA, and claim that AS is reserved only for the Prophets, and therefore, it is incorrect to use it for the Imams?
All Muslims used to refer to Imam Ali and Fatima Al-Zahra and Imam Hasan and Imam Husain as AS. You can ask your friend to read Bukhari book where he can find him referring to Ali as AS عليه السلام. Till today, there are big Sunni scholars refer to Ahlul Bayt as AS.
‘We are the real followers of Quran and the Prophet and find in Quran Salaam on true believers and no one doubts that Ahlul Bayt (AS) are the best believers.
Wassalam.