They're equivalent. If at least 1 participant is unreliable/dishonest and I don't know which one, the only logical reaction is to treat them all the same until I can determine the culpable one.

Perhaps, but it feels a bit like the Monty Hall paradox/game. If you know which ones are more truthful, then the odds aren't as bad as "everyone must be guilty until proven innocent."

"Innocent until proven guilty," the modus operandi of the US judicial system, at least in theory, is the design of a system that assumes trust and removes offenders.

It's not about "justice" or "fairness". It's about "correctness". An "honest" agent with stale data is as unreliable as the "dishonest" one.

When dealing with Byzantine-style problems, there is no such thing of "who is more truthful?", just "what is the consensus that should be agreed on?"