bbp_make_spam_user( int $user_id )

function bbp_make_spam_user( $user_id = 0 ) {

	// Use displayed user if it's not yourself
	if ( empty( $user_id ) && bbp_is_single_user() && !bbp_is_user_home() )
		$user_id = bbp_get_displayed_user_id();

	// Bail if no user ID
	if ( empty( $user_id ) )
		return false;

	// Bail if user ID is keymaster
	if ( bbp_is_user_keymaster( $user_id ) )
		return false;

	// Arm the torpedos
	global $wpdb;

	// Get the blog IDs of the user to mark as spam
	$blogs = get_blogs_of_user( $user_id, true );

	// If user has no blogs, they are a guest on this site
	if ( empty( $blogs ) )
		$blogs[$wpdb->blogid] = array();

	// Make array of post types to mark as spam
	$post_types  = array( bbp_get_topic_post_type(), bbp_get_reply_post_type() );
	$post_types  = "'" . implode( "', '", $post_types ) . "'";

	// Loop through blogs and remove their posts
	foreach ( (array) array_keys( $blogs ) as $blog_id ) {

		// Switch to the blog ID
		switch_to_blog( $blog_id );

		// Get topics and replies
		$posts = $wpdb->get_col( $wpdb->prepare( "SELECT ID FROM {$wpdb->posts} WHERE post_author = %d AND post_status = '%s' AND post_type IN ( {$post_types} )", $user_id, bbp_get_public_status_id() ) );

		// Loop through posts and spam them
		if ( !empty( $posts ) ) {
			foreach ( $posts as $post_id ) {

				// The routines for topics ang replies are different, so use the
				// correct one based on the post type
				switch ( get_post_type( $post_id ) ) {

					case bbp_get_topic_post_type() :
						bbp_spam_topic( $post_id );
						break;

					case bbp_get_reply_post_type() :
						bbp_spam_reply( $post_id );
						break;
				}
			}
		}

		// Switch back to current blog
		restore_current_blog();
	}

	// Success
	return true;
}