"Little girl" was a better insult than "piggy" not simply because it's more thematic but because it's more realistic. Bullying is often gendered and sexualized.
There might be a couple of things to mind here. One is that LTROI's "piggy" might be more than you think because this isn't the Anglosphere, and (knowing nothing of Swedish culture or values) it could be that porcinity has connotations for Swedish folk that don't occur outside Scandinavian cultures. Another is that we're talking about Blackeberg (and Los Alamos) forty years ago.
Fifty years ago in my little corn patch there was a worse thing to be called, a word beginning with 'p' and rhyming with 'wussy". Just about the only thing worse would be words imputing homosexuality, one such word starting with an 'h' and another starting with an 'f'.
Owen doesn't say "little girl" to be bigoted -- he's simulating the power of his own bullies. While his "but you're a girl" comment was arguably misogynistic, Oskar also expresses doubt (at least in the book) when Eli promises to fight his bullies.
It's not bigotry. It's sexism (although we could go 'round and 'round the mulberry bush a few zillion times about what the actual difference is).
Again, remember, this was set 40 years ago. Ellen Ripley (Alien, 1979: in space, nobody can hear you scream) had only started making the rounds three years prior on the Big Screen - she who chucked H. R. Giger's creation's phalliform head out the window of a deep space life pod - and while she most definitely blazed a trail for other tough, smart and independent leading ladies in mainstream theater and
everyday life, the message was still taking a while to start breaking glass cielings. Ripley wouldn't establish herself as a Marine's best dream and worst nightmare for another seven years, how's that for "slow"?
Some five or six years earlier, when I graduated high school, the implicit assumption schools (and most of the rest of society) being foisted on children was that boys would grow up to be farmers and construction workers, and girls would grow up to be cooks, baby factories and housekeepers. Anybody who wanted anything beyond this was either rich or kinda weird, or maybe both. At the time, if anybody had tried to suggest that a twelve year old girl with Abby's physique (or Eli's) could chuck Kenny's head out any kind of window would have been laughed right into an asylum: Kenny out-massed her by almost half, and none of the difference was flab.
Even if Abby's physique had been greater and/or Kenny's less so, there's probably another component to Owen's weakly offered objection: having her fight his fights for
him would have had pretty much the whole school calling him the dreaded P-word with a solid subtext of "coward".
Depiction isn't the same thing as promotion. A storyteller's responsibility is not to appease everyday sensibilities when depicting everyday evils, especially in horror. The movie is meant to feel uncomfortable.
A storyteller's responsibility is merely to entertain, but an exploration of the whole concept of "entertainment" would probably wind up trying to go places where the moderators on this board would nail up a sign saying "ROAD CLOSED". Just as a suggestion for where such exploration might begin, our forebears gathered around the fire and told stories about things that happened on the hunt while they huddled in caves at night, and while their stories probably usually involved a lot of laughter, it just as probably often involved tears when hunting forays incurred casualties. They weren't just gloating about their successes or mourning their losses, they were also indirectly analysing all the coulda-shoulda-woulda scenarios in an effort to get a better grip on their prey and on strategies for maximising yield and minimising loss. Einstein didn't invent "thought experiments", some brute lugging around a cudgel did.
"Successful" storytelling happens when buttons get pressed. Blatty and Friedkin (Exorcist, 1973) pushed religious terror, Stone pushed the horrors of war (Platoon, 1986) and King pushed (amongst other things) the horrors of childhood (It, 1986 novel) with liberal supernatural (symbolic and/or metaphoric) inclusion. We have many buttons to push, so the "top ten" of just about any given list of works of fiction is going to have different kinds of button pushers. Lindqvist also pushed some buttons pretty darned hard and we're still
trying to figure out exactly what those buttons are after all these years!
On another note, the impracticality of Owen's knife is raised in the movie. "What are you gonna do with that?" his bullies asked him. When I saw him use it against the tree, I couldn't help thinking "don't break it, kid!"
The very first word to cross my mind when Owen tried to brandish it in Kenny's face in the locker room was "impuissance".
On top of the thematic elements I talked about, it touched the romantic feelings I had as a kid.
There was this girl named Debbie when we were in the seventh grade, eyes like scintillating blue diamonds in the night, hair the colour of espresso, laughter like a symphony of silver flutes. Her whole body shook when she laughed, and she laughed often
. I was at that age already, when I noticed other girls I tended to notice body parts rather than the girls themselves, but when Debbie invaded my dreams, eternity wrapped itself around my heart with millions of promises of cinnamon rolls fresh out of the oven, long, lazy days on tropical beaches just running my nose through that wonderful lustrous hair
Romantic feelings? You betcha