Well, IMO he is probably gonna get convicted on both. States that have a brandishing law, as Virginia does, can pretty well state if you can see the firearm and you are in an argument, then you were brandishing. Here is the law on brandishing:
18.2-282. Pointing, holding, or brandishing firearm, air or gas operated weapon or object similar in appearance; penalty.
A. It shall be unlawful for any person to point, hold or brandish any firearm or any air or gas operated weapon or any object similar in appearance, whether capable of being fired or not, in such manner as to reasonably induce fear in the mind of another or hold a firearm or any air or gas operated weapon in a public place in such a manner as to reasonably induce fear in the mind of another of being shot or injured. However, this section shall not apply to any person engaged in excusable or justifiable self-defense. Persons violating the provisions of this section shall be guilty of a Class 1 misdemeanor or, if the violation occurs upon any public, private or religious elementary, middle or high school, including buildings and grounds or upon public property within 1,000 feet of such school property, he shall be guilty of a Class 6 felony.
B. Any police officer in the performance of his duty, in making an arrest under the provisions of this section, shall not be civilly liable in damages for injuries or death resulting to the person being arrested if he had reason to believe that the person being arrested was pointing, holding, or brandishing such firearm or air or gas operated weapon, or object that was similar in appearance, with intent to induce fear in the mind of another.
C. For purposes of this section, the word "firearm" means any weapon that will or is designed to or may readily be converted to expel single or multiple projectiles by the action of an explosion of a combustible material. The word "ammunition," as used herein, shall mean a cartridge, pellet, ball, missile or projectile adapted for use in a firearm.
As for the Obstruction of Justice charge, that law is pretty broad and can be widely interpreted:
18.2-460. Obstructing justice.
A. If any person without just cause knowingly obstructs a judge, magistrate, justice, juror, attorney for the Commonwealth, witness or any law-enforcement officer in the performance of his duties as such or fails or refuses without just cause to cease such obstruction when requested to do so by such judge, magistrate, justice, juror, attorney for the Commonwealth, witness, or law-enforcement officer, he shall be guilty of a Class 1 misdemeanor.
B. If any person, by threats or force, knowingly attempts to intimidate or impede a judge, magistrate, justice, juror, attorney for the Commonwealth, witness, or any law-enforcement officer, lawfully engaged in his duties as such, or to obstruct or impede the administration of justice in any court, he shall be deemed to be guilty of a Class 1 misdemeanor.
C. If any person by threats of bodily harm or force knowingly attempts to intimidate or impede a judge, magistrate, justice, juror, witness, or any law-enforcement officer, lawfully engaged in the discharge of his duty, or to obstruct or impede the administration of justice in any court relating to a violation of or conspiracy to violate � 18.2-248 or subdivision (a) (3), (b) or (c) of � 18.2-248.1, or � 18.2-46.2 or � 18.2-46.3, or relating to the violation of or conspiracy to violate any violent felony offense listed in subsection C of � 17.1-805, he shall be guilty of a Class 5 felony.
D. Any person who knowingly and willfully makes any materially false statement or representation to a law-enforcement officer who is in the course of conducting an investigation of a crime by another is guilty of a Class 1 misdemeanor.
So, bottom line, when the guy decided to take a stand and was arguing with the supervisor (right or wrong), he opened himself up to being charged with the brandishing. And, then arguing with the Sheriff's Deputy got him the OoJ charge. If you notice, no charges were filed for illegally carrying a firearm, as he was totally within the law on that one.
This is another reason I think OC is a issue. I came from an Open Carry state. Prior to CHL and motor vehicle carry, if you had a loaded handgun in your car it had to be in plain sight. We also had a brandishing law, and were trained as I mentioned above. I do know of a case where a guy and his ex-girlfriend's new boyfriend were in a verbal altercation. The former boyfriend had a handgun laying on the dash of his car in plain view. He never threatened the new boyfriend, but police were called and the old boyfriend was charged with peace disturbance and brandishing, and he was subsequently convicted of both.