Anonymity is among the chief features of the internet -
you, bukena, have discovered another key feature: when arguing on the internet, one should bear in mind the person at the other end of the argument may be neither as dumb nor as inmpotent as you assume him to be.
If you have any recourse at all in this circumstance, it is with Yahoo; see what you can accomplish through Yahoo's member support facillities.
Oh, and don't get your hopes up real high.