Deniers

12 clues
Naysayers
Disputants
Gainsayers
'Nay' sayers
Suspects, usually
They just say "no
Contrary claimants
They won't admit it
Measures of yarn fineness
Group with no admittance?
Units of fineness for yarns
One side of the climate change debate
Similar answers:
Abadending
Abraceofdentists
Acaseofidentity
Accessdenied
Accident
Accidental
Accidentalbreak
Accidentally
Accidentlog
Accidentphone
Accidentprone
Accidentreports
Accidents
Accidentsarewaiting
Accidentshappen
Acidentals
Aciers
Actingpresident
Addend
Addenda