We cannot resolve all these disagreements definitively. Infamy opens questions about how we solve political crimes, especially when we do not have direct access to evidence. In that case, we decide which authorities we trust, and which we do not. For virtually all crimes, we cannot possibly conduct our own primary research, conduct forensic experiments, interview witnesses, observe past events, examine crime scenes first-hand, or even read reliable accounts of the crimes. Everything we do to find truth independently, apart from trustworthy authorities, requires time and resources we do not have. Thus we rely on others to investigate and report back.
The heavyweight authority in politics is government. Aside from its legal authority, and its use of coercion to enforce laws, government persuades people about the nature of political crimes through its inherent claims to legitimacy and respect. If you are a skeptic - that is, if you distrust government's claims, because they come from government - you have to decide which other authorities to respect. Infamy takes up these two violent, brazen and apparently inexplicable acts from a skeptical standpoint. They do not make sense in any other light.