I imported favorites from IE, and lo and behold a bookmark entitled PORN or adult or something was there, and in this bookmark were subcategories of all the different porn genres. There were no links to web sites, just the categories and subcategories all conveniently ready to use as bookmarks.
Errr, well, if those bookmarks exist in IE, then it will happily import them for you, regardless of what they are. Did you check to see if they existed in IE when you imported them?