If you can not dump them, you can use these patterns in any editor that supports regexps(e.g. Notepad++ in Windows, jEdit in Win/Mac/Linux). Just extract all files and folders from epub, open all the html/xhtml files in the editor, and use replace operation on all opened files:
Find:
Code:
^(\s*)(<p[^>]*>)(.*)</p>\s*$
Replace: