Master Stoker,
I see two seperate issues here. One is the problem of the individual you spoke of, who appears to have an attitude problem or is egotistical. Only those who witness what you have can determine that, and even then it might be a false impression or a misunderstanding. If his demeanor is of a high self worth in all situations, you might just want to be polite, and avoid direct contact outside of the Dojang.
The second issue is about the use of titles and maintaining a senior to junior relationship in everyday settings. If a higher ranking Black Belt, or Master is of the mindset that teaching continues outside the dojang as well as in, and they believe that it is "proper" to use the titles regardless, then it might not be an attitude or ego problem on this particular issue (other things might reveal an ego, but this might not be one of them).
I know that some people disagree with this concept, but I was trained that it is proper respect to always address your Master Instructor by their title and last name. It is not by "demand" of my teacher, but through an understanding of the reasoning. When I was younger, I would see my instructor (a 4th dan) at a mall or somewhere. I would stop, bow, and greet him just as I would do in the Dojang. Today, he is an 8th Dan and I would never call him anything but Grandmaster, no matter what the setting.
I have been to social events with Korean Grandmasters where 6th and 7th Dan bowed their heads in restaurants, bars, and bowling alleys to an 8th Dan, calling him Kwanjangnim, and the 8th Dan did the same to the 9th Dan. They could be drunk on sake and soju at 2:00 in the morning, yet when the older Grandmaster spoke, all of the other Grandmasters would stop talking and say yes sir! It is their culture. Senior is senior 24 hours a day. I was raised to call my Dad's father "Grandfather," or "Grandpa." I would never have called him by his first name when speaking to him. I don't think it was wrong, or that he was arrogant because he taught that kind of respect.
Personally, I don't agree with the "buddy - buddy" concept between students and Black Belts, or Black Belts and Master intructors. There is an instructor / student relationship that I believe should not be crossed. Be friends with your contemporaries, other Black Belts of the same rank, or non Martial Artists. I had some adult students one time who liked to get drunk, and wanted me to party with them. They wanted to be "buddies" and call me by my first name. I politely declined and said that this was not my purpose with them. I was their teacher, and that should remain so inside the dojang as well as out.
This is my opinion. It is how I was taught, and what I believe in. I respect others who do not, but that way is not for me. As you know, I always refer to you as Master Stoker, because you are a Master Instructor, and I feel you have earned the title. You couldn't get me to stop calling you that if you tried - lol

However, I do not expect the other members here to do the same, and I do not feel they are wrong if they don't - this is just my way of doing things.
Respectfully, :asian:
CM D. J. Eisenhart