Kid freaks out and squeals, wife screams "stop screaming!" How do I handle it?

We have two boys, one is almost 4, the other 1.5. My wife is a SAHM and I work remotely at home. The younger one isn't good at sharing or boundaries yet and often takes things from the older one and generally harasses him because he wants to play. That's not a concern though; he's just young and he is making progress as he develops. The issue is that when the older one gets frustrated, he starts squealing and using a loud high pitched voice telling the younger kid to stop. It's pretty obnoxious, but he's still learning how to handle his emotions. My approach to this situation is to calmly move the two out of reach of one another and to try to calmly de-escalate the older child and redirect the younger one. It generally works pretty well and I can usually calm the older one down quickly.My wife does that sometimes, but she has a tendency to try and overpower the situation by yelling instead. For example, just a few minutes ago, the older child was in the bathroom using the toilet. The younger one entered the bathroom, as he often does, and wanted to play. The older one is not ok with being touched while he's on the toilet and starts squealing things like "Don't touch me! Leave me alone!" My wife's first and only response was to yell "OLDER ONE! STOP! SCREAMING! NOW!" and repeats variations on that until she's removed the younger one from the situation and the older one calms down. I'm working at home elsewhere in the house and I can hear the entire exchange very clearly.I'm not sure how to address this with my wife. Whenever I hear her yelling at the kids like that, it makes me really anxious. I don't like it and I don't think it's an appropriate response to the situation. Trying to get a kid to stop yelling by yelling at them seems like it's just going to teach them that raising their voice will get them what they want; they just have to be the loudest. I'm pretty sure I know where this is coming from. It's her mother. I've heard both my wife and her brother talk about "how mom would yell and scream at us when we were kids." I've seen my MIL get angry a handful of times, and shouting is her go-to move.I haven't said anything to my wife regarding my feelings about her yelling at the kids, and honestly I'm afraid to. Whenever I try to have civil discussions about anything uncomfortable, my wife gets really passive aggressive and ends up ultimately shutting down with a "whatever" and ceases to engage in the conversation. That's exactly how her dad responds to confrontation.I'm not sure what to do. Anyone been in a similar situation? Any advice? via /r/Parenting https://ift.tt/2FlWh8R