I agree with your sentiment, but any unnecessary energy use is still wastage and still needs to be generated, leading to pollution, even if the carbon footprint is smaller than when using coal power plants.
In this case, every kWh spared by your data center still is a potential reduction of carbon emissions : let your hydroelectric power plants run at full power so they still provide this kWh, thus it doesn't have to be produced by the carbon-emitting power plants. Leading to reduced carbon emissions.