thanks for all your comments. I see now how a comment can be so different when it's coming from someone who really understands the situation an OP is having and those who don't.
I haven't been in your clothes, exactly. But all dojos that don't have beginner classes have to deal with this: how to teach and how to organize things so that the demands of all levels are met.
I've taught in a small dojo where I mostly had beginners plus one 3rd kyu student. After one year I realise I had put most of my effort on the beginners, and not given him enough time and attention.
I've been in dojos where we trained with the same partner the whole class, and the more advanced students were assigned the task of taking care of a beginner. Some of the advanced students loved it. Some were mildly unhappy about the situation but didn't feel they could complain... there is much to learn from teaching beginners - I like it, I even started a small university dojo in order to be able to continue doing it. But like in everything else, people are different. For some people it takes more time to appreciate working with beginners. But usually, I'd say that's not really expected at shodan. (Then there are those who LOVE teaching a beginner since they can spread their ego all over the poor beginner. It's not always those who are most fond of training with beginners who do the best job at it)
I've also trained at dojos where everybody took care of themselves, and chose training partners only to their own benefit never thinking about the good of the dojo. This can sometimes create good aikido, but never happy dojos.
So I've wrestled with these issues, a lot! from different perspectives.
Stories like Eva's, and dojos I've seen where by some funny coincidence most of the advanced students drop out when they have to spend too much time taking care of beginners, tell that your feelings are not that unusual. That people pass harsh judgements on you is unevitable, I think. They follow the general aikido/budo norm. But I do think that some people here could consider what Jun has written about moderating the tone of one's posts.