I don't think anyone is questioning that, only if freezing people is remotely standard procedure.I don't have a quote to hand, but I'm pretty sure either Lucas or Kasdan has said that the intent was for carbon freezing to be a known practice, only the crude nature of Cloud City's facility (presumably because it's only meant for inanimate or at most, non-living organic cargo) raised questions of suitability.
I agree that most everyone acts as though it's risky only due to Cloud City's facilities, but the one line that is hard to make fit is Lando's, "Lord Vader, we only use this facility for carbon freezing." Well no shit, Space Sherlock. That's what we're here for.
Unless he means that they use it to freeze carbon, as opposed to using it to freeze other things in carbonite.
