If the copy becomes distracting in the design then you are doing something wrong or they are discussing copy changes. It might be a bit annoying but you could tell them that that discussion would be best suited for another time. At worst the discussion is at least working towards the final goal of your site where questions about lorem ipsum don’t.

I’ve heard the argument that “lorem ipsum” is effective in wireframing or design because it helps people focus on the actual layout, or color scheme, or whatever. What kills me here is that we’re talking about creating a user experience that will (whether we like it or not) be DRIVEN by words.