After the second Punic War, Carthage had been severely reduced in power and influence. It certainly was no longer a threat to Rome. This vindictiveness did not make sense to me.
Twice was enough, I think, for a good many Romans. Carthage would undoubtedly produce another son or cousin or nephew or some other convaluted relation of Hamilcar or Hannibal who would, of course, take up arms a third time.
It was time to nip it in the bud, so to speak.