Then the matter is sooo simple. Give him the quotes and he can confirm what they mean. Simple.
And I don’t see why you find what has been said in the quotes so difficult to accept if you truly do Itiba. That is what the Imams said. Do Itiba. Do not simply accept what we say until you know from where we got it? Why the fuss then???
PS: Good to know you actually have spent time studying Arabic. Very good to see.