We know Zahards an asshole. What we don't know is weither or not V was. And he wouldn't have been killing Baam because of his fathers sin. He'd be killing him because of what his father built him to become.Yes, could be - but that would mean that Zahard is an asshole / child murderer nonetheless and not the king that defends his territory because he has to. Killing a child because of his fathers sin? Again, Bam would have needed time to grow. Enough time to figure something out that doesn't involve killing Bam.
Gustang's comment already pretty clearly says that he, subjectively, considered V to be a worse person than Zahard. So that part isn't really in doubt. The question is why would Gustang think that.