When I came across it, I went sort of nuts. I had worked very hard for my culture and was not happy about possibly having to give it up. As it turns out, it is a "declineable" quest, and I would suggest that you do just that. There is no advantage to the quest, and absolutely no downside. It will not come back to haunt you. In all of the discussion that went on at the time, not one experienced player advised me to complete the quest. You may, at any time decide you want to do some house-keeping with your culture, but it should be on your terms. Again, I suggest you decline/skip this quest.