Anthony was making out it was a logical argument that should have been applied to Paul once Meg was murdered, but it wasn’t actually logic, it was all about suspicion.
People were suspicious of Ash, and suspicious of Meg - so thought there was definitely one, and probably two traitors in the dungeon.
It was pretty much 50/50 whether to save Andrew or Paul, and they went for Andrew.
They thought that left Faithful Paul in there with potentially two traitors (in which case Paul was absolutely doomed).
Ash was then banished, so they were proved right about one traitor.
They thought that left Faithful Paul and probably Traitor Meg (as they were still really suspicious about her) - in which case Paul was done for as he was the only choice for murder.
Instead it was Meg that was murdered. They had to reassess, as now it looked like it was Faithful Paul and Faithful Meg, and actually there had only been one traitor in the dungeon after all (Ash).
They were proved wrong about Meg, but that didn’t mean Paul suddenly had to be a traitor (and up until then no one really suspected him).
The lingering question niggling away at everyone ever since is why did the remaining traitors murder Meg instead of Paul.