Without knowing the details, I'd reccommend discussing (usually on his/her page) why you believe your edit is valid, backing it up with valid references. If the editor ignores your reasoning, contact another editor of the same article to see if he/she might agree with your reasoning. Never lose your cool (which can be very difficult at times) and seek out an admin (at WP:LOA) for assistance. The intervention may not be immediate, but that's how I'd start.