I think most places would view such a refusal as grounds for disciplinary action against the lawyer.
New Zealand for example has legislation to address this: https://www.legislation.govt.nz/regulation/public/2008/0214/latest/DLM1437864.html
There can be good causes to refuse a client, conscientious objection is not one of them.
Assigned seating has been the norm here for decades. Makes things go a little more smoothly, especially when everyone expects it.