And here I was, hoping for a clear-cut answer! Seems some people mind, others don't.
Again, I wouldn't object to a new gun being fired in principle, but I would expect whoever fired it (factory or gunshop) to give it a scrub, simple courtesy. The other two new S&Ws I bought were probably fired a few times, but at least they were clean, allowing me to experience the full "new gun feel".
In this case, however, it really seems like it was fired after I inspected it and purchased it, without my permission. And whoever did so didn't bother to clean it. Definitely not a sign of repect. I'll call over the week-end, see what comes of it.