Completely remove vanilla Wordpress tags and categories
//Remove categories and tags
function unregister_categories() {
register_taxonomy( 'category', array(), array('show_in_nav_menus' => false) );
}
add_action( 'init', 'unregister_categories' );
unregister_widget( 'WP_Widget_Categories' );
function unregister_tags(){
register_taxonomy('post_tag', array(), array('show_in_nav_menus' => false));
}
add_action('init', 'unregister_tags');
function remove_tagmenu(){
remove_menu_page('edit-tags.php?taxonomy=post_tag'); // Post tags
}
add_action( 'admin_menu', 'remove_tagmenu' );