Of course he's stealing. Think of the commercial. A young woman buys a burrito and it flies out of her hand and on to the street when her jerk boyfriend hits a bump in the road. A Taco John's employee gives Whiplash a new burrito to deliver to her.
So where did he get this burrito? Did he pay for it out of his own pocket because he felt sorry for the young woman? Yeah, right. I'm sure Taco John's employees make so much money they can afford to buy new burritos or tacos for everyone who drops one. So, obviously, the employee is stealing from the restaurant.
And don't forget that after delivering the new burrito, Whiplash engages the cops in a high-speed chase. Do you think a monkey with such low moral values really cares about whether or not the food he's delivering is stolen? Whiplash is a hard-core criminal, a menace to society. It's no wonder that Diggler thinks he's cool.