Obviously you need to use whatever chart that you see fit to use, but I think you missed my point.
Clearly you can't display negative values on a pie chart.
The point is that a pie chart is designed, however poorly, to display all the parts of a whole, and their percentage of that whole.
If you have data with negative values, even if you exclude those data points, the data is not fit to display in this manner as it is not representing a whole at all, and a bar chart is the more logical way to go.
Again - FWIW
Just an observation.