Blaming the teacher

I have a question concerning how I should react when one of my student (I’m a teacher) blames me for his result (when obviously he didn’t understand something and I’m pretty sure my teaching was good since 95% of the others got the question right).
Usualy I try to explain to him his error, but often it doesn’t make it, and he keeps arguing and not taking responsability, saying it’s because of the question that wasn’t clear, or me… and, yes, i do feel somehow insulted and my thinking goes to « I have to prove I’m right, and justified in my jugement… » I get that i can’t change him and that’s what students do, but in that case, I just can’t tell him he is right (you often say we have to find how the person is right to let go of the confrontation mode)…
Thank you!