Wait, really?
Interesting...looks like this is a cultural difference. I mean, a slap on the shoulder or something, sure, but a slap to the face, outside of very particular situations (such as breakups, for example)?
That's a grave insult, to me. I mean, it's kind of the last border of civility. You're forsaking words for violence--that implies that you are no longer worth talking to. It's not quite cutting ties, but it's pushing it.
Admittedly, I'm extraordinarily old fashioned, when it comes to manners. Maybe such things are less important than I thought, nowadays?
I think we can call cultural differences. In
my personal experience, the adults
I've seen (that I've interacted with, there's all sorts) tend to impose less restrictions on their kids, and be more comprehensive. So at least, on the 'old fashioned' thing, I can give my opinion that things
have changed. In some places.
Each group of friends has their own way they relate to each other. What one can see as a breach of civility, someone else might not even blink at.
I've seen kids who almost never hit each other, and kids who are constantly hitting, slaping, punching each other (and laughing. And trying to separate them is nigh impossible.) As an adult, I can look and feel maybe those kids need to play fight with each other in order to discover and rediscover their own strenght, their own bodies.
Now... as far as 'particular situations' go, IIRC, we had just (accidentally) implied that we had unilaterally, as judge, jury and executioner, hunted down Oriko and maimed her for the crime of setting fire to Sayaka's house. Like, Oriko burned Sayaka's house down, we broke her arm and neck. Implications. Implications that, I think, would seem like a horribly miscarriage of justice, and a horrible abuse of power to Hitomi.
To be completely fair, while we're friends with Hitomi, we haven't been friends for
long, we haven't had lots of moments where we set rules as to how we interact we each other. This was such a moment, I think, but... not in a "we believe it's OK/not OK for friends to slap each other in X situations" way, so much as a "slapping is not OK... because we're meguca and that triggers our supernatural fighting instincts so it's supernaturally dangerous".
Sort of an external imposition. Sabrina's and Mami's instinctual reactions were
way out of line.
Hitomi trying to slap us almost caused us (or Mami) to hurt Hitomi really really badly, but that was because magic. Same as Sayaka breaking Table-chan.
EDIT: Somewhat ninja'd?