If NPR's primary source of support is to come from large businesses and philanthropic organizations, then the network will be forced to take a pass on reporting on possible misdeeds by these organizations, their officers, and/or their shareholders.
I referenced that in another post. There's no connection between funding and news gathering. Because their funding is so diversified, they can afford to take a pass on the funding rather than ignore an important story.
Many assume that business leaders will do the "right thing" ethically when push comes to shove but history tends to paint a bleaker picture.
In this case, the journalists at NPR are more focused on reporting the news than appeasing their corporate sponsors. The emphasis on listener support is what gives them that power.