My opinion, you are right in how you feel and they are 100% in the wrong. In fact, there IS no excuse. Even if it is a meeting or discussing training, why would another belt - someone who is also interested in learning not be welcome?
This is my #1 complaint about martial arts. In fact, you run into this in any organization where you assign hierarchical ranks, associate authority to them, but do not provide people proper training in how to execute their rank. NO RANK exists without the rank under it and no rank exists without the ranks over it (if this require clarification, please let me know). People who abuse their own rank or mistreat those under them in my opinion, do not deserve their rank. I don't care if you are the greatest martial artist on the planet, if you can't show respect to someone who you outrank, as far as I'm concerned, you are no better than the white belts who are you abusing.
I seem to have a unique perspective on this being in the military. I know that several of you are also in the military, and I frequently wonder if it is just me, if it is an Air Force thing or if you guys are annoyed too. I've been to a lot of different dojos and have seen this in many places.
In the military, you live with your rank every day and the lives of people above and below you depend on your ability to use that rank and authority properly. The problem is, when you only get your rank for a limited time, there is far too much temptation to misuse it. People who aren't used to it sometimes like the power that it gives them and enjoy that separation. As far as I'm concerned, the relationship between a black belt and a kyu should be no different than that of an officer and enlisted. You are certainly allowed to be friendly, just not friends. There is nothing wrong with having a few beers with your officers, in fact, the good officers would welcome the chance to get the pulse of the troops.
Here's my story - there was a guy in my organization who I ran into who acted like this - refused to talk to anyone who wasn't another black belt, would stop people from half way across the room to make them bow, mistreated and talked down to lower belts. The guy was a live at home 24 year old kid, talking down to people twice his age and "forcing" them to respect him. Though he was a higher ranking belt, it got me to the point of breaking and I pulled him aside and in no respectful terms, counseled him about the use of his rank....luckily in this case, it caused a marked improvement. That may not happen with all, unfortunately....but it apparently works with some. I've also run into some VERY young (teenage) black belts in which the problem was VERY bad, the issue is that no one ever pulls them aside and tells them what a jerk they are being. The bottom line is that we are all people, your rank means nothing more than a time in service and ability designator, it does not give you free reign to mistreat anyone.
I'll be happy to go tell them that they are being jerks!