One reason it might be a reductio ad absurdum is that it suggests that in an election in which supporters of one side were rational (and thus would not vote, since each of their votes would have a minuscule chance of mattering) and the others irrational (and would vote, undeterred by the small chance of their vote mattering), the irrational side would prevail.
If this is the claim that John G. Halstead is referring to, I regard it as a throwaway remark (it’s only one sentence plus a citation):
For instance, a simple threshold or plausibility assessment could protect the field’s resources and attention from being directed towards highly improbable or fictional events.
One reason it might be a reductio ad absurdum is that it suggests that in an election in which supporters of one side were rational (and thus would not vote, since each of their votes would have a minuscule chance of mattering) and the others irrational (and would vote, undeterred by the small chance of their vote mattering), the irrational side would prevail.
If this is the claim that John G. Halstead is referring to, I regard it as a throwaway remark (it’s only one sentence plus a citation):