Why, he's a freaking weirdo.
I get it even though, logically, I know he's not a good guy.
It's obvious his father abuses him and makes unfair demands of him. Luna was his only solace since childhood and he's delusional in that she always will be despite his own behaviour. He's like a kicked puppy that keeps going back to an abuser... It's hard to watch. He trusted her words foolishly and basically confessed his guilt, which is definitely going to result in his dad beating him worse than usual. He's not a good guy but it's hard to absolutely despise him when you know he only acted in this specific instance like that to avoid his dad beating him into the ground.
Tldr: he's scum but doesn't deserve the abuse his father will put him through after this trial.
I understand your point
Not gonna lie, I kinda do feel bad for the dude tho