He told me once there was no place for him in the world, that he didn't fit in anywhere. He really was off the scale. Boy by day, girl by night. Except, he was a girl all the time, inside. (6.31)
Society totally looks down on people like Luna—people who don't necessarily fit the mold. Because of this, Luna feels like she'll never belong.
The whole gender role expectation thing was too confusing to me. Why couldn't people just be accepted for who they were? (6.36)
People are seriously jerks sometimes. Instead of just accepting everyone for who they are, they end up judging people—like Luna—who aren't hurting anyone.
Yesterday I might've smacked him. Or laughed. Today? What difference did it make? The world was all wrong, skewed, out of natural orbit. We could never be close. (9.3)
Regan has a few prejudices of her own, namely that a popular boy will never be interested in her. Chris definitely proves her wrong on this count, and also shows her that he can be understanding and sensitive too. Swoon, right?
I quelled my rising terror. We'd just be two girls out shopping. Who would notice? Who would care? Who would even look at us twice? (8.86)
Unfortunately, even though Regan thinks that people are probably not going to notice them, people do pay attention. And they react negatively when they see Luna.
I wished I could forget. Those punks. The clerk. The punks' reaction could almost be expected. It didn't prey on my mind as much as the clerk. The moment she saw what Luna was, when she physically repelled away from her, that feeling seared a scar on my soul. (12.33)
The public's reaction to Luna doesn't just hurt her—it also hurts Regan to see the kind of prejudice that Luna will have to deal with on a daily basis. People won't change their minds right away.
He slowed and stood for a moment, staring. The expression on his face—God. Disgust, loathing. I don't know what it was, but it made me cower in fear. (13.99)
Things are pretty rough when people catch sight of Luna. Even though she's not doing anything harmful, people seriously look at her as though she's subhuman or something.
"You're not welcome in our home anymore, Regan. And your brother… My God, he needs help." (19.19)
All this time Regan was convinced that the Materas were so kind and progressive, but it turns out that they have the same prejudices as so many other people. They don't even want Regan or Luna to ever step foot in their home again.
"I only wanted to try on a dress." His voice went flat. "They didn't need to call security." (20.84)
Luna does some seriously harmless things—she goes to try on dresses, eats tacos—and she just wants to be treated like a normal human being in the process. Instead she's treated like a criminal just because people don't understand what it's like to be transgender.
Hoyt screeched, "You f***ing pervert!" Loud. It attracted the attention of a couple of girls who were clomping down the stairs. Hoyt jabbed Luan's shoulder again and yelled, "Perv! You're a perv. I always knew it." (22.115)
Hoyt's always been pretty mean to Liam, but things escalate when Liam comes to school dressed as Luna. It's as though Hoyt now has a reason to seriously treat Luna in an inhumane way—as thought Hoyt needed the excuse in the first place.
It scared me, this whole transition thing. Every time she went out in public I was terrified what people might say or do. Hoyt. Others like him. What if the violence extended to me? The bigotry? And hatred. (23.22)
It makes sense that even though Regan wants to support Luna, she's afraid of the backlash from her transitioning. After all, people have been pretty harsh so far—it's not like they're going to stop being completely prejudiced against Luna and her family.