Here is what I would say to Sunnis. Don’t tell them the Imams control every atom in the universe. Tell them that Sura Naml verse 40 teaches us that the one who had some knowledge of the book was able to do something supernatural by God’s permission. He transported the huge throne of Bilqees from Yemen to Palestine in a second. And Sura Ra’d verse 43 speaks about the one who has the knowledge of the book (meaning the full knowledge), who is Imam Ali. The Prophet also said that his family of the Ahlulbayt never separate from the Qur’an, which means they possess all the knowledge of the Qur’an.
So if someone can do supernatural things by having some knowledge of the book, why is it problematic or blasphemy the Imams were also able to do supernatural things given that they had full knowledge of the book?
I would discuss it with them in this manner.