My parents had some truly epic fights, and they did do it in front of me and my brother. The first one I clearly remember was when I was 4-5, and it ended with my mom upending the leftover stew over my dad's head.
This was not one of the happier elements of my childhood. My folks were good, loving parents in most respects, but my dad had a temper, and both my parents knew how to pick, pick, pick at each other (and at us kids too). I wouldn't have minded being sheltered a bit more from their marital problems, especially the parts of them that spilled over onto us kids. They did get into counseling eventually, and that helped.
I don't mind some of the other things I wasn't sheltered from, however. My dad had a crude sense of humor and swore like the proverbial drunken sailor. And they were both very open with us about the biological facts of life, and they discussed politics in front of us and so on. They didn't place many restrictions on our TV or movie watching or on our reading (they were cross when they discovered that my cousin and I had sneaked some reads of some very sexually explicit and rather, um, kinky, books we found in her parents' bedroom closet, but I think it was more embarrassment on their part and disapproval over us snooping through their stuff than anger over what we'd actually read).
This all rendered me very non-squeamish and pretty hard to shock later in life, which has mostly been a positive thing, I think.
My brother maybe had a different experience with the latter stuff, though, because he and his wife have been stricter with their three girls. They wouldn't even let them watch roadrunner cartoons when they were grade school age (too violent), and they warned the rest of the family that there was to be no swearing or talking about things that were connected to sex or discussions about unpleasant political stuff in front of the kids. They were concerned that The Hobbit and LoTR were too violent for them as well, and that the later HP books.movies might be too scary.
I completely agree with his decision to refrain from yelling (and hitting) though. If I'd had kids, I would have tried to do the same, which probably wouldn't have been too hard, since my husband and I never scream at each other or lob personal insults when we disagree/argue. At most, one or another of us might get a bit snappy or short, but it's always followed by apologies. His parents had some nasty fights too, and unlike mine, they ended up getting a divorce.
I think that it's okay to let kids see their parents disagreeing, even arguing, sometimes if it shows them that people who love one another don't always agree, and that it's possible to have disagreements without being destructive.