bbp_remove_topic_from_all_favorites( int $topic_id )

function bbp_remove_topic_from_all_favorites( $topic_id = 0 ) {
	$topic_id = bbp_get_topic_id( $topic_id );

	// Bail if no topic
	if ( empty( $topic_id ) )
		return;

	// Get users
	$users = (array) bbp_get_topic_favoriters( $topic_id );

	// Users exist
	if ( !empty( $users ) ) {

		// Loop through users
		foreach ( $users as $user ) {

			// Remove each user
			bbp_remove_user_favorite( $user, $topic_id );
		}
	}
}