If the copy becomes distracting in the design, then either you’re doing something wrong or they’re discussing changes to the copy. It might be a bit annoying, but you could tell them that such a discussion would be best left for another time. At the very least, this discussion is working towards the ultimate goal of your site, whereas questions about ‘lorem ipsum’ do not.

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