Is that still true if the costs of oil/gas stop being socialized? Basically the people pay for oil cleanups, for air polution, etc, the cost is still there it's just not currently born by the oil companies. Also, how do the costs stack up if you drop all oil subsidies?

It's saying that society pays a price for fossil fuel emissions, in terms of damage to our climate and our health. Millions of people die every year from fossil fuel emissions. If we attach a price to that death and destruction, and apply that as a cost towards fossil fuels, it makes the financial subsidies of wind and solar insignificant.

I don't know much about wind power economics so you should certainly not take my "tacit" word for it.