No, he wasn't. He didn't treat that man with respect, he violated his constitutional rights, he terrorized a mother and her child, and he disgraced his uniform. All for some money from a fairly obvious speed trap.
The foundation of our society is the equality of all of our citizens under the law. The professionals among our law enforcement community understand this and control situations with firmness but courtesy.
This officer was wrong and demonstrated poor judgement and callous disregard for his responsibilities.
A lone officer, a young man not obeying the officers instructions, a young man walking back toward a vehicle the officer hadn't searched, a young man making movements toward his pockets when the officer hadn't searched the young man.
I would say the officer has a justified concern for his safety.
Could he have handled the entire affair differently and/or better?
Sure he could have but we don't have the option of do overs.