I would state my case, to the membership, that the constitution cites a non-denomination position. I would propose that any denominational "leaning," (in this case a RC mass), is inappropriate. Further, if the membership persists, and won't remove the RC persuasion, I would make it a point to change the leadership. Then, if they won't change, I would start a non-denominational group. I suspect that you'll get quite a crowd in the new organization.

PS: I face a very similiar situation in the SE USA, only here it is
    fundamentalist protestantism!!!