Once you restore all the blog posts, you can go in and delete just the offending blog posts and comments, using a query like this
Code:
UPDATE `forum`.`blog_text` SET `state` = 'deleted' WHERE `blog_text`.`userid` =7870
and
Code:
UPDATE `forum`.`blog` SET `state` = 'deleted' WHERE `blog`.`userid` =7870;
just change the userid to the correct one you want to clean up.