Many people hated Klaus without even knowing him and Marcel was selfish in himself which didn't have anything to do how Klaus raised him. Marcel was just good and pretending to be good, Klaus never cared what masses thought of him, he only cared how his family and friends thought of him. Marcel literally stole what Klaus had built in New Orleans(when he made a deal with Mikeal) and then blamed Klaus for wanting it back. It was never Marcel's kingdom it was Klaus's (whom Marcel conspired to run out of the home he(Klaus) made).
Eshal Khan his life turned him that way, from the abuse to the heightened emotions first from his werewolf nature and then his vampire. Klaus may be considered evil from those who don’t know him but others know that Klaus life made him ‘evil’. But if that is what you believe... I respect your opinion.