You're absolutely right.
It's possible that a nuclear war might have just the opposite effect of a nuclear winter, it might cause a runaway greenhouse effect. It might also do nothing, the earth's built-in feedback systems might be able to eventually buffer out the change of conditions. I do not know what the effect of a nuclear war will be on climate (although I suspect there will be one!). I don't think anyone can tell that at our present state of knowledge of the atmosphere.
The point I was trying to make was that the post I was responding to was based on poor logic.