Hey again, Bella

In this kind of situation, I think the 2 most important things are:
- do not escalate the situation,
- keep your boundaries.
Your boyfriend shouldn't call you dumb or yell at you. When my boyfriend has an anger outburst and start raising his voice or being disdainful, what works best for me is to say something that will both validate his feelings and put boundaries.
Example: "you are raising your voice you called me *insert nice word that popped out*, that makes me really uncomfortable [observation], you seem to feel upset/angry and I understand [validation] but I don't want to be talked to this way. [boundary]"
At that point he may still feel too angry to react positively, so what I do then is leave the conversation to reassert my boundaries, by saying something like "I don't want you to talk to me like that, so I'm gonna go to the other room/go back at my place and we can talk later when the emotions are cooled down."
Usually with my bf it works well and he comes to me to apologise when his emotions have cooled down, but that really depends on the people. I used to try and appeal to his common sense in those moments and eventually learned that it's a waste of energy and is more likely to make things worse. When emotions are too high, the rational brain barely works at all and there's no use trying to reason him. He needs to cool down first and in the meantime you don't have to be around. ;)
What do you think?