So, what's the problem? Does the presence of dirt on the windows reduce the value of the photos, or eliminate it altogether? Is the presence of that dirt a good reason not to display the pictures? Of course, they're small on the screen (you could click through to my Flickr site and see larger versions). The dirt would be more prominent in 8 by 12 prints.
Would the photos be purer and thus better without the dirt? For that matter, would they be more or less interesting without the dirt? That's a different question.
These questions are ethical and aesthetic ones. They are aesthetic because they have to do with the desirability of the images. And they are ethical because the images imply something about the world.
Should I wash the windows and retake the photos? Would I gain anything by doing that? Would those pictures be better, or just different?
On the other hand, I have no desire to play with gray scale versions of these photos. The color is important.