- I don't appreciate the idea of not being able to change the dojo,
You just started there. You don't have the right to "change the dojo". You have the right to pick your teacher, you have the right to pick your dojo. If you do not like what is happening there you have the right to leave, in fact you have the responsibility to leave. No teacher wants to have people there who are not happy being there.
Moreover, this seems like a very corrosive lesson when applied to other facets of life outside of the dojo.
I don't know how you think the world out there works but this is a perfect lesson for life outside the dojo. You will have bosses you don't like, you will have customers you don't like, you will have jobs you don't like. You can suck it up or you can leave. You think anyone in your corporation is going to give a rats ass if you don't like the management style of your boss? You want to change the company, then stay long enough and work hard enough to get promoted to the level at which you have a say so. It's pretty much the same with a dojo.
You want to tell the sempai you don't like the way he orders you about? Go ahead... he might even tell you he's sorry and he'll be nicer... maybe. Or maybe he'll tell you "tough luck". You don't have any say so here. If the teacher wanted things to be different, he would do something. He may actually be doing something about a senior who has let his ego get in the way of his training or the good of the dojo. But if you don't see the teacher doing anything about it, then he's probably ok with it. Then you get to decide to stay or not.
If there are issues of inappropriate levels of violence and injury in a dojo, you should leave. If a teacher is manipulating the students for his own benefit, you should leave. If there is sexual exploitation occurring you should leave. But having your feelings hurt because a senior was brusque with you, didn't ask you politely enough when he told you to do something... well, it seems to me that's his problem and you should suck it up and get on with your training. This is Budo and having your feelings hurt because a senior treated you as if you were of little consequence isn't a cause for much gnashing of teeth and rending of garments. Maybe the guy is a jerk... that is his problem and you should get over it. It is certainly not your job to reform him. That's the teacher's job. On the other hand if you just wanted a fun place to pursue an enjoyable pastime, you should leave immediately because it sounds like this place is going to push your buttons.