People go "Eat the Rich" all the time but when it's a cute girl they're all "Oh No!" Either way, this is more (relatively) 'harmless' and misguided bullying from a kid whose in a really shitty life situation lashing out towards someone they really like (given the tons of context clues, and the many chapters of him outright trying to ask her out) without realizing it's not what they should be doing (since they're a kid in a shit point of life and judgement isn't usually great) because they're far-far-far more well off than him, and actually have success and a good home life, which is what he obviously covets and wishes for.
I'm not really a defender of bullying, even here, especially when it's physical or goes too far too often, but I can genuinely think of worse things Oscar could do to her, like trip and harm her as his friends jokingly recommended which he had the conscience to not do . Having context and the 'why' for said bullying is happening is just as important as the bullying itself. Teenagers are fucked when it comes to brain chemistry and clear objective thinking and hormones. Oscar has at least demonstratively shown that he's long past evolved and grown from his teenager self and regrets it, albeit with a now seemingly guardian-syndrome and is now overprotective of Flora. Besides, this comic always ends on cliffhangers and just gives probably ~75% of the information for tension and growth, so there's a really good chance there's way more to the bullying and the head spaces than we see.