Well Bitfinex seem sure of their own reasoning but let's face it, if they were competent it would be 1:1.
They messed up their preparations - there is no way unsettled margin positions should impact on other users, that loss should be maintained between Bitfinex and those in the red. They messed up bad.
If I got 1 BTC in my account I should get 1 BCC, end of story. Nice to see Bittrex have got their shit together.