I certainly agree that deleting a fact type should also strip away any of its columns out of People View. In addition, there are probably a couple of other management issues for PeopleView that could be improved.
One that I've thought about for a long time (and I think I've submitted as a wish list item) is that it would be helpful if you could save People View setups - which columns are displayed and in which order - sort of like having a library of the setups and picking the one you want without having to redo everything. But to tell you the truth, my thinking has evolved a bit in this regard. I seldom want more columns in People View than will fit on the screen anyway because People View loses a lot of its value if you have to scroll to the right. It's really easy to add two or three columns to People View without actually saving the setups. And my experience with Named Groups and saved Custom Reports is that very quickly I have so many items saved that I can't remember what any of them do anymore, and it's easier to make a new one than it is to find the one I saved. So in the last year or two, I find myself just deleting all my Named Groups and all my Custom Reports and starting over again. Strange I know, and probably not very satisfactory to most of you all. But I'm sure that if a new facility were introduced to have a library of People View setups, I probably wouldn't use it.
On the other hand (and sort of related to Tom's observations about what happens when People View includes a column for a deleted fact type), it would really be handy for a single button and single click just to clear People View so I can easily start all over. Indeed, I really wouldn't even want it to ask me any silly questions about whether I really wanted to clear People View. I would just want it to clear People View with one click. I'm sure most users wouldn't like that feature, either, but I think it would be great. So in the interest of reducing clickiness and also still protecting the user from themselves, what if the "clear People View" button existed and what if if had an Undo option associated with it?