1. How is what Paarthurnax has supposedly done in the past, any worse than what the other dragons have done, let alone worse than Odahviing, who they apparently don't have an issue with despite him being allied with Alduin far more recently, and he also obviously is not the pacifist type like Paarthurnax.
2. The actual crimes themselves. The blades are incredibly vague about the issue, they don't even bother going into detail about why what he did was actually so terrible, or what he did at all to earn him such infamy. We also can't question Paarthurnax or Odahviing on the matter either, so we don't get much of an explanation from the blades, and we can't get differing perspectives from the one being accused, or from a third party.
3. It is presented as a strict ultimatum, based on an oath that again, is not explained to us in its actual meaning, and also goes against their previous oath to our character, yet somehow supercedes it.
All in all, it doesn't feel very much like an actual dilemma to me, so much as a cheap, and forced attempt at creating a dilemma.


Or rather, "dragonguard".