Need Advice...Off topic... Teacher got in my son's face

My son came home and told me his teacher got in his face and yelled at hom calling him a liar several times. My son has accommodations due to a physical limitation with handwriting that was granted by his school district. This teacher denied him this accommodation and I (not my child) reported this. The teacher was approached and said he didn't deny him his accommodation, except for a particular assignment which is in fact a denial right? Instead of simply admitting this he yells at my son in his face so loud the other kids in his middle school class asked my son what he lied about. I am furious! I feel my son was verbally abused, bullied and intimidated by a person in authority whom he should be able to trust. My first thought was to go straight to the principal but I have taken a few days to calm down abd still angry but uncertain as to the correct approach. This happened once before with the same teacher... He growled in my sons face. I approached the tracher who said he didnt mean anything by it.

Please advise me... My son struggles in school as it is. I dont want to make it more difficult nor do I want to pretend it didn't happen. On the matter of denting him his accomodation the teacher wrote me an email stating I need to go to him "before believing a child" and I was angry at his condescending attitude.