Lightning vents out her frustration on Snow (and Sanctum) too. Where is all the Lightning hate? She's a total bitch, too, and blames Snow for things that are just as much her fault, too. So, ehm, let's start a hate Lightning faction too, okay? Then it's fair.
Lightning vents out her frustration on Snow, Hope on snow, Vanille on herself, Sahz on himself and so on. Most of them have somebody they complain about or hate against. Hope's just one of the many.
He's a teenager who just went trough something terrible (purge, death family, braded a l'cie, hated by the world, loss of humanity). He's confused and frightened, and tries to cope with his feelings. In no small part thanks to Lightning, his way of doing so is by turning his feelings to anger and hate, and directs it at Snow. This is not unrealistic, I've seen other teenagers do the same. So yeah, maybe he unrightly blames Snow. So does Lightning. And in fact, blaming someone unrightfully happens all the time in real life. It's realistic.