Using clientside_validation project, default validation plugin message not being overridden for states dependent field
Turns out this is a bug. The hot fix is to add the $message argument to the _clientside_validation_set_equal() call on clientside_validation_fapi.module. So that it looks like: 
_clientside_validation_set_equal($name, $title, $params[0], $js_rules, $message);.

I've started an issue and submitted a patch https://drupal.org/node/2140163