Nothing you can do, but it also doesn't matter. Since he's not in your trust list, no one can see his rating unless they click "show untrusted feedback." Almost no one does that, and many trustworthy people on this forum also have "untrusted" neg. ratings (people who out scammers, for instance).
TL;DR: Don't worry about it.
Thanks for your respond.
Perhaps you are right ... I just wanted to have only + trusts :-) and this crazy guy r00t$ messed it up.. for no reason ...
Yes ... I wil try to not worry about :-)
Thx again for cheering me up a bit.