One bizarre argument that has come up on Twitter and amongst the media recently is that George Osborne, in his ruthless free market zeal, is determined to privatise RBS, selling off some of the government's stock now, despite this meaning the government will have lost money by rescuing the bank. According to these critics Osborne fails to see the obvious correctness of their arguments and the obvious stupidity of this move because he is blinded by an ideological obsession with privatisation. This line of attack is nuts. Firstly, you do not make a loss when you realise it; simply turning the equity into cash does not suddenly mean the government has lost out. By analogy: imagine I buy a house for £400,000, but I accidentally drive a bulldozer into half of it, meaning that it is now worth only a quarter of what I paid. When did I get worse off: when I drove the bulldozer into it, or when I sold it? Am I still worth £400,000 until I sell the house for its new value of £100,000?
Secondly, even if you did, there's little to no reason to expect RBS shares to rise above any other asset in the future; the government could easily lose more than the notional £12bn less its 79% stake is worth than when it was bought. There may well be some market inefficiencies (or perhaps not) but even if there are, no one is seriously going to argue that the government is playing one of the super-sophisticated strategies to exploit those inefficiencies by holding onto a FTSE100 bank that it picked up as part of a bailout.
Thirdly, simply comparing price now to price then is ridiculous: the FTSE as a whole has something like doubled since 2008 and 2009 when RBS was bailed out. If the relevant counterfactual is 'risky equities investment' then the government could have made tens of billions of pounds; if the relevant counterfactual is 'pay down debt' it could have saved billions of pounds on debt interest. On a more relevant comparison, the state has lost a lot more than £12bn. But it lost that when it invested and when the price fell.
If it's bad to sell off RBS, that's because there's some special reason why RBS will do better for itself and society if owned by the government. This is quite implausible; actually it seems more likely that owning RBS could twist governmental and RBS incentives, distorting the banking market and harming society overall. It is complete nonsense to say that by selling now Osborne is losing money for the Treasury—it's already gone.