My problem comes with the Klingons NOT being a reforming power by any means (if anything they were decaying with corruption, being so entrenched in their system) and yet somehow still being Federation allies despite the fact that this WHOLE time they've been conquering, pillaging, and generally gone a'viking like those dudes in a Capital One ad.
(My opinion of Klingons:
Yet the Cardassians were actually taking real steps to FIX and CHANGE things in a better direction. If the Federation is so big on democracy and freedom--the choice should've been obvious. But instead they went with the unconscionable "ally."