function eugene_ges_block_external_items( $retval, $type ) {
    // if item is an external rss feed, stop it from recording in GES
    if ( $type == 'exb' ) {
        return false;
    }

    return $retval;
}
add_filter( 'ass_block_group_activity_types', 'eugene_ges_block_external_items', 10, 2 );