however, there could be some kind of initiative from blockchain's perspective to somehow map fraudulent public keys with private ones and freeze them. I do understand this is not easy to filter legit fraud cases and not to blame the innocent ones, etc etc but something should be done regarding this issue.
Public key cryptography is based on the premise that it is not feasible to compute a private key from its corresponding public keys. If that could be done, the entire Bitcoin concept would become unusable.