Oh, this happens, of course. I think I wrote somewhere that when I've attended seminars without a hakama and wearing a white belt, quite a lot of people (mostly mudansha) seemingly spend a lot less care during training towards me (ie not focusing on me while they're uke, ignoring the fact that I bowed to them at the beginning of a technique). I can't say it's the norm, but it happens.
OK, from the way I was reading things from the start of this thread, it sounded like something different. I got the impression that people were being treated poorly, simply because they weren't a certain rank.
i think this happens alot no matter where u go. many seniors just wanna practise at a certain level and dont wanna deal with the newbies. btw i dont support this view. often i force myself upon them and seek them out when a senior ignores. then i let him feel how a "newbies throws" or reverses their technique. all while just simply smiling at them