I have always felt sympathy for him. He's twelve for pity's sake. I teach kids who have social problems and bad home lives. I see what it can do to them, lots of pent up anger, lashing out, a desire to cause pain. They lack decent role models in their home life and it's very hard to give them a set of boundaries and social skills in the few hours you see them in per week. Imo, a child is 'innocent' until the age of about 16/17. That's when they have to take all they've learnt and become an adult. Joffrey was never given the chance to do this because he was made king at twelve, long long long before he was ready.
That may be, but he shot people, with a crossbow, who were demonstrating because they were starving, forced people to duel to the death, was going to have Dontos killed for being unready to take part in a tournament, had Sansa stripped and beaten publicly, had Ned executed instead of being sent to the Wall as the adult parties had agreed on, and a whole shopping list of lesser transgressions.
You may sympathize with Joff, but don't be shocked that you're in a distinct minority.