He has the worst motive for being vigilante, he even beats Laurel in that.
So some thugs beat him on the street, (and I am sure he had been beaten a lot in his life, because that's reality) and he suddenly is into violence and playing a hero on the street. He is a smart, genius guy, can't he just helps the team and the city by being smart and genius. Why the smart people in these shows need to prove that they are heroes by doing the physical fighting.

He is the male version of Felicity.

He talks way too fast sometimes but its only a minor annoyance.