Society charging legal fees for case against builder as per house size

Our Cooperative Society has 100 members having different sizes of flats from 1BHK to 5BHK. In order to fight the builder/developer of our Housing Society (on account of non provision of Clubhouse, Swimming Pool, OC, etc. as per commitment) the society collected "Legal Charges" from each member. They decided that the charges would be levied depending on the size of each flat. Consequently, owners of 1BHK flats pay the least while 5BHK owners pay the most. Since a majority of owners are of smaller flats, this decision was passed by the AGM. My contention is that all members should bear legal costs equally since all flat owners would equally utilize the facility of Clubhouse, Swimming Pool, etc. and benefit equally from the legal fight against the builder. The Society insists on charging me interest (since I have not paid the legal charges) on overdues. I've conscientiously and regularly paid all maintainence and service charges, other than Legal Charges. Please advise on the correctness.