Great post. Especially the part about abuse vs assault.
Like you said the Bellamy/Octavia incident wasn't an every day occurrence which is why the others jumped in and tried to stop her. The Arkers might have handed down strict sentences (floatings and lashings) but fighting like that isn't something that is a part of their culture. I don't think anybody would have stopped two grounders from fighting. So it definitely is the warrior culture
And last night I was watching S1 clips and after Charlotte jumps the first thing Bellamy did was go after Murphy and start to beat him up. So he did the same thing as Octavia which is why he understood it.