Mark, the Helsinki agreement did not only apply to outside aggression but the active destabilization of states. The quick recognition of Slovenia and Croatia was an act designed to destabilize Yugoslavia and encouraged civil war and this was a civil war regardless of the internationalization that took place with recognition.
I would agree that those two were the first dominoes. Again, you may well be right. Yugoslavia was, after all, a relatively new entity: each of the Federated republics was its own entity prior to the 20th Century.