Is there any reason deflation would reduce profits?
For some models, deflation makes consumers save more, because they expect one unit of money in the future to buy more goods than one unit now. Consumption falls, so revenue and current profits fall. 

The fall in demand and profit may have feedback effects: less investment, less innovation. 

In general, depends on the model you are using. In a static model with homogeneous firms, the real profits may stay unchanged.