Similar to the E-2 question, how would you react to a young 2LT who is being unprofessional with a strong sense of entitlement?

Remember that everybody has a boss.
Use the chain of command to get this Lt's attention

I provide my ID and remind/inform the lieutenant of the regulation or policy that governs headsets (presumably 670-1 and post policy), and request (under general authority) that they(?) comply with the appropriate policy. Should they fail to comply, or become belligerent, I would offer to allow the MPs to address the issue and that they could work out the finer points of selective compliance with their chain of command - a COA that is not likely to appeal to the lieutenant.

Every now and then I had to let an officer know he was an officer and gentlemen by an act of Congress and that I respected the rank on his collar but any other respect he or she had to EARN.

As with the E-2, unprofessional is unprofessional no matter what. Ask to meet with the 2LT and remind him or her of their role and how they are currently being looked at as being. A good Officer would respect the meeting and take notes to be a better leader to produce better followers.

I would report it to his command and if that don't work I would go old school ?

Once upon a time, I watched two fighter pilot First Lieutenants brace and ream a buck sergeant (dates my service, yes?) for failing to salute them on the walkway into the BX.
When they finished. I said in my quiet command voice, learned from my O-6 father, "Lieutenants. A moment please."
After the turned and observed my silver RR tracks. I said "where are your covers?" As expected, the leader responded "we are pilots and do not wear them on the flight line". I said "Correct but have you lost your way?" The answer was "What Sir." I then pointed out that the BX was a 1/2 mile from the flight line. And inquired how they were going to get there coverless. Both responded "Buy a new one, Sir." I said "Good plan. Don't forget your rank insignia." Then after a two count, I said "There's more."

I then pointed out a unforgivable lack of situational awareness for an officer. "Are you aware that it's mid-december, the sergeant was carrying 2 bags of obvious Christmas decorations, and his wife was next to him carrying a small infant." When they said "No, Sir" I remarked ... so . . . you would miss a "Flogger" [MIG 23] coming out of the sun too. No response to that. So I dismissed them.

I was a JAG officer (line in the AF) and expected to get some chaff but silence ruled.

With respect if possible find an Ofgicer of higher rank to handle it. If not note name and unit take a pic for evidence and go see their CSM

I once corrected a young 2nd LT. For having his hat on sideways and his shirt unbuttoned. Stated to him about AR 670-1 and how dare me as a JR. NCO correct him on his wear of the uniform and I did let him know about general military authority and he just rolled his eyes and finally said to me, SERGEANT!! It's the end of the duty day so who really cares. The wayward LT. Wanted to know who my commander was so I told him and where my unit was too. I was called into the commanders office the next morning with the First Sergeant, Captain, CSM, LTC, and the wayward LT. I explained to my command as to what occurred the day before and the LT said that's how it happened. Needless to say, I thought my LTC and CSM were going to have a stroke. My COC thanked me for a job well down and said that will be all Sergeant and close the door on your way out. I did see the LT try to stand up, but my BC told him, NO, YOU WILL STAY, and we will have a discussion as to why AR 670-1 applies to everyone 24/7. Needless to say, that LT got his ass handed to him by my COC! They were pissed off and passed news of the incident to his COC! That LT didn't have a good day. Yes, I was only an E-5 (P), but was always willing to call out uniform violations. I made an on the spot correction on our Division CSM, but he would walk around jacked up at times just to see who would correct him and I got a 4 day pass out of the deal. Another time, I spotted a LTC hurry out of a building without his hat on and I respectfully reminded her she was out of uniform because she didn't have her hat on. She was embarrassed, but thanked me for stopping her and got another 4 day pass out of the deal. So, new LT's are not above being corrected by any rank.

1968 Americal Division Chinook company.A major was transferred from another Chinook company to our company to become our new Commander. I heard him say He was going to get another R&R even though he had one at his previous company. ( only 1 R&R per year tour) I contacted a NCO at the division R&R office, they canceled his not authorized R&R. I later heard him say someone does not like him !!

In any case, the recommended procedure is as follows:
1. Obtain evidence of the infraction. A photo is good; most cell phones have a camera. Motion video is best, but in this specific case a photo will work
2. Politely inquire the LT's unit, unless you know what it is; in that case, confirm it ("Are you in the...?")
3. Identify the infraction; do it quietly and if the LT acknowledges and corrects (or maybe even just acknowledges) end of story
4. If LT's response isn't professional or the LT refuses to correct, get the heak away and proceed to...
5. Proceed to LT's unit (recommend the Shirt or A1), show documented evidence, ask if this meets their standards (no name-calling, no finger-pointing, keep it professional)