It's not that parents are destroying kid's brains when they yell, it's that they are changing the way the child's mind responds to that stimuli. They are pushed into fight, flight, or freeze mode which means the child may freeze up (which may anger the parent even further and cause more anger to be unleashed), fight the parent back by yelling, hitting, biting, or run away from the situation. All of which, if the parent doesn't understand this biological aspect of the child's functioning, can make the parent even more angry at the child and can increase the level of punishment the child recieved. What's important to note here is that the child has very little control over these responses as their system has already read the parent's yelling as an attack and the parent as a source of danger. This was a video I found pretty helpful in explaining this: https://youtu.be/dnjBaOyJWU0
Now, there are moments where yelling become a neccesity. If a child is about to walk off the edge of a cliff or into a busy street or in someway are threatening their own well-being or someone else's, those are moments when yelling to get the child's attention would be acceptable, even absolutely neccesary, to save a child's life or prevent harm to themselves or someone else. But often, parents yell to express anger or get their child's attention or to train them to behave in a certain way and this pretty much boils down to an expression of control over the child; this is not healthy nor contributes to an effective relationship. These actions tear at the parent-child relationship and keeping that relationship healthy and supportive is an important step towards creating a relationship that both parties benefit from and a kid remains responsive to.
The encouraging thing is that moments of anger that occur in an otherwise healthy relationship have been shown to NOT incurr the sort of long-term damage that repeated yelling and verbal abuse can cause. Parents are human and they will mess up, get angry, and lose their calm at certain times. That is not what any of the research and these articles critize. What they do take issue with is yelling as method of exerting control over children and repeated yelling used to keep kids in line. Rather than "keep kids in line" it actually increases misabehavior or causes the child to just shut down phsycially and emotionally. The emotional, relational, and psychological damage of this is hard to calculate and is best avoided.
Some helpful articles that cite some good research on this topic: