Arguing /fighting in front of kids

How do you handle this if it happens? Every couple sometimes argues right? What happens if it happens in front of kids? Sometimes arguments get out of hand and turn into fights with yelling. I grew up with parents fighting and I hated it. But i as i grew older I hated the fact that my mom didn’t stand up for us kids or herself? She says it doesn’t help the situation but not speaking up hasn’t helped either because it makes the bad behavior ok?