I'd probably just stand there and watch and try not to recoil in terror. I may allow it to be obvious in my face that I'm taken by surprise or maybe distressed. I think people generally--almost everyone--would be absolutely averse to visibly showing distress or fear or humiliation, because of the ego, even if they really do feel those things. It's kind of sad that people can't interact in a genuine way and show their vulnerability or be 'small' and not worry about being psychically tall relative to others. Life would be so much better without so much ego and callousness, people could support each other so much more, on certain, important levels.
Of course, to be fair when you're yelled at it's not always for a valid, legitimate reason so recoiling in fear or shame could cause an injustice of sorts. It would be nice if people were smart enough, reflective enough, self-critical enough or sensitive enough to realize when yelling at someone is unwarranted and unfair.
I'm not really sure if people suppress their natural reactions to being yelled at, or if they just have no reaction because they're so callous and unempathetic that it doesn't even bother them that somebody right next to him is lividly angry. People seem generally unempathetic and callous to others, like they're dead or something, or maybe just like others are dead to them. I guess they're just not really connected to the core of life and virtue, it seems that most people are kind of "slag" in a sense (but not only for this reason, there are other reasons too, such as being unintelligent, not thinking independently/engaging in group-think, not having integrity, being way too concerned with their egos, and having little moral integrity. Some of those attributes may be contributing factors to their being unempathetic to others, such as being unintelligent, which is like having mental or psychic deadness of a sort.)
Of course, there is also the factor of people typically developing what they call a "thick skin" because of how often they're unduly abused by the many assholes in life, that could also help explain it if people are actually emotionally unfazed, or largely unfazed, by being yelled at. It's kind of fair to have a thick skin because of all the assholes in the world, I guess, but I don't relate to it and I lament living in a world where everyone is thick-skinned.