For this to lead to a net negative, it has to be more than just a lost opportunity to make energy: either it is a significant energy consumer (i.e. not just a dissipater), or the turbines must be incapable of producing significant amounts of energy even when working correctly. There is something that has not been explained here.
That the turbines were incapable of producing significant amounts of energy even when working correctly, is not out of the really of reason.
How bad would it be to insert a comment about regenerative braking here?
But yeah, that sounds so bizarre. The Emperor's New clothes territory.
Regenerative braking is not an issue here. Wind turbines slow down the wind to generate electricity, so, in a sense, they are always doing regenerative braking when operating as intended. They would only be mechanically braked when this (and also blade feathering) is insufficient or inapplicable for some reason.