I always encourage people not to jump to conclusions when a player is charged! The Brett Stewart case surely was enough for folks to realise an early media report may be nothing like what actually happened when all the evidence is out.
As to the charges, from memory Amone was charged with a 'reckless' offence, meaning you know your action might result in harm and you do it anyway. Manase's was intentional, no surprise given it was plunging a knife into someone's back. 'Oh I'm awfully sorry, i thought you were my medium rare steak'.
You can take it up with parliament if you like, they consider 'intentional' more serious then 'reckless' (max penalties 25 years vs 14 years) 🙂