Brian, technically you raise a fair point about the nature of current wind subsidies. But correcting it leads to further complications. If you prefer to compare total cost of ownership or lifecycle costs, you have to do it equivalently for all alternatives. For one, nuclear power's costs also tend to be front-loaded: construction is expensive but fuel and operating costs tend to be modest. The Breakthrough Institute has published a number of articles recently arguing that nuclear power is significantly more cost-effective than solar or wind. And it effectively is carbon-free too, so that argument does not apply.
Beyond that, comparing net present value of energy options requires making assumptions about future financial, policy, and other factors that are fraught with uncertainty. Subsidies are created by policies that can and do change -- or fail to -- in ways that differ from official rhetoric. Financial crisis led to subsides for renewables being cut back in some places sooner than expected. Other subsideies, e.g., for biofuels, persist despite broad political support for eliminating them. Negative public attitudes sparked by the Fukushima disaster caused some countries to freeze or undo nuclear power development. And so on. The existence of such uncertainties itself imposes a risk penalty on current investment decisions.
So your assumption that wind subsidies, for instance, will remain targeted on 'capacity building' may not be reliable. 'Mission creep' and inertia are not unknown in public policy. Once a constituency dependent on government subsidies acquires sufficent mass, it is likely to lobby to maintain or add subsidies for whatever rationale will work.
Consider the Price-Anderson Act, designed to indemnify utilities that bought nuclear power plants, which was passed in 1957. Wikipedia notes: "The act was intended to be temporary, and to expire in August 1967 as it was assumed that once the companies had demonstrated a record of safe operation they would be able to obtain insurance in the private market." You may have noticed that 56 years later, the subsidy is still around, despite a great deal of nuclear power capacity having been built in the interim.
In Virginia, where I live, politicians have been arguing lately -- next year there's an election here -- that it's time to repeal a much-disliked gross receipts tax on businesses. The tax was originally imposed to help pay off debt from the war........the War of 1812.
Schalk's essential argument remains valid: A notion of 'grid parity' which compares costs of solar/wind power under ideal conditions to the costs of conventional power under real conditions is fundamentally erroneous and misleading. The intermittent, unreliable nature of solar and wind and some other 'renewable' power options imposes a negative risk premium that utilities must and do factor into real decisions. Even subsidies cannot remove the tangible costs of backup or storage.
Hence, you conclude that "the entire argument for renewables is silly if you don't value carbon." But that is overly simplified, and not really true. If you do value carbon, nuclear power looks like a more cost-effective option. So too does traditional hydropower -- which effectively is as 'renewable' as anything else, but which many environmental activists insist is not.
Alternately, there are other reasons -- social, political, economic, environmental, strategic -- to make a case for renewable energy sources, even if carbon is not considered at all. In the US, the Solar Energy Research Institute was established by Congress in 1977 during the Carter Administration. (I was one of its first employees.) At the time, there was little interest in global warming -- if anything, many scientists were warning of the threat of global cooling. The main reasons for the policy goal of the Carter administration to expand use of renewable energy focused on oil dependency and the lingering threat of another OPEC embargo. That, and a popular view within an increasing influential environmental movement -- stoked by Amory Lovins among others -- that nuclear power was dirty and dangerous. Those concerns were further inflamed in 1979 by another oil embargo and the Three Mile Island accident.
Those issues persist today, along with concerns about air and water pollution, acid rain, oil spills, mining accidents and many other interests that affect energy policy, completely unrelated to global warming or carbon emissions.