How do i remove all Bit.ly shortened links from site?

This can be solved by making SQL queries directly in the database. But this only works easily for replacing the URL of a link, not the whole link markup. Replacing all bit.ly links with their original long URL would be the best way to solve the blacklist problem. This is the query you would do, for example in phpMyAdmin or whatever you’re using to access your database:

UPDATE wp_posts SET post_content = REPLACE(post_content, 'http://bit.ly/oldlink', 'http://newlink.com/newlink');

But if you want to completely remove the link so that only the anchor text remains, there’s not much you can do except regex filtering the content with preg_replace:

<?php
/*
Plugin Name: Remove bit.ly links
Description: Plugin to remove all bit.ly links from post content, keeping the anchor text.
Version: 1.0
Author: Matthias Kretschmann
Author URI: http://mkretschmann.com
*/

// Filter the_content
add_filter('the_content', 'rbl_remove_bitly_links');

// Le function
function rbl_remove_bitly_links($content)
{
    // Regex, FTW!
    // Search & remove link markup for all links
    // with bit.ly, j.mp or bitly.com as href attribute
    return preg_replace('@<a[^<>]*href="(?:http://|https://)(?:bit\.ly|j\.mp|bitly\.com)[^"]*"[^<>]*>@Uis', '', $content);
}

This looks for all domains bitly is using, feel free to reduce that to the set you need. You can put this into a new php file in your wp-content/plugins folder and activate it. A more lazy way would be to add this to your theme’s functions.php file.

Please be aware this won’t really remove the links from the database, so they will still be visible in the editor. They just won’t appear on the frontend.