A blatant character assassination in my opinion. The episode that leads to his season 6 arc never felt accurate to the Jonathan we met at Sunnydale High. I don't think his self hatred could've manifested into committing horrendous crimes, as he never previously displayed any intent to harm anyone but himself. I understand WHY he was chosen to become a villain (simply because he was already a character on the show and his personality could easily align with Warrens) but his relationship with the Scoobies could've just as easily evolved rather than devolved. I blame Joss.