Why is religion negotiable and not the other cases?
The wheelchair is not negotiable because the guy in it, doesn't have a choice.
Religion is not negotiable, if the religious person says so.
The dojo rules are not negotiable, if the teacher says so.
I don't see a problem here. Religious people don't have some sort of right to be taught aikido at their own terms. Aikido teachers don't have the duty to accommodate everyone.