gistfile1.php

// the required fields that we want to ignore
//$safe_fields = array('field_test2');
//just grab all fields in the second field group
$safe_fields = $form['#groups']['group_option2']->children;

// get a list of all errors
$errors = form_get_errors();
// this will clear Error msg queue
$messages = drupal_get_messages('error');

// clear all errors so we can add all of them back except the ones we are trying to clear
form_clear_error();
if (count($errors)) {
  foreach ($errors as $field => $msg) {
    $field_name = substr($field, 0, (strpos($field, '[') - 1));
    if (!in_array($field_name, $safe_fields)) form_set_error($field, $msg);
  }
}