<human>: We've been together for about 2 years. 

We don't fight very often, but I've also found he feels the need to raise his voice when we're discussing or debating something (this is not at all in an argumentative way, for ex: is chocolate or vanilla better type of thing). 

When we do fight, he screams the whole time and won't let me get a word in. When I finally do get a chance to explain myself, he COMPLETELY breezes over it and keeps repeating himself, even if I explained the thing he's repeating. I do not respond well to screaming, it scares me and I completely shut down. I have asked him, every single time we argue or debate things, that he needs to lower his voice. He used to comply and at least try (usually ending up screaming only for me to remind him again) but now he won't and refuses to because "that's just who he is". I've asked him why he feels the need to scream and he said it's because, growing up and living with such an outgoing and loud family, he would have to scream to be heard/get his point across. I've told him that he does not have to do that with me, that I'll hear him out better if we have a calm, polite conversation, that I won't interrupt while he says his piece, etc. He's also told multiple times he's "always right". 

I know exactly what he's doing. His screaming is assuring that I won't be able to get a word in, he knows I'll shut down and stop trying to explain, therefore, he's "right".

Although we don't argue often, having a constructive argument is a very huge thing for me. I want to be able to be heard and have my feelings understood by my partner in a calm, civil manner. 

How can I help him to act more calmly and understand how big of a deal this is to me? Also, how do I deal with his constant need to be right?

Could you distill the essence of the text into 1-3 sentences?
<bot>: SO feels the need to always scream and be "right" when we argue. I don't like yelling and shut down. I want to know how I can help him get over himself and have more constructive arguments.