The plugins overview correctly replaces the uninstal link of a plugin with dependents with a note. For the same activity plugin the activitiy management page displays a delete link and no dependencies indication. In both cases you can delete a plugin with installed dependents although in the plugins overview you would have to enter the url (both the uninstall and delete go to the same place).
Is this an issue to anyone? Quick googling didn't find any tracker issue on that.