It is true that NPR received a generous gift from the Kroc family ($200 million in 2003, http://www.washingtonpost.com/ac2/wp-dyn/A6973-2003Nov6?lang...). However, in that same year, NPR's operating budget was $100 million. Assuming a generous 5% utilization of that endowment, that would only pay 10% of the budget.
In fact, NPR's web page states that it receives a little under 10% of its annual budget from "major gifts," while nearly a third (the largest single fraction) comes from pledges and annual memberships. (see http://www.npr.org/about/privatesupport.html)
I guess your statement that listener donations are "a fraction" of NPR's operating budget is true. One third IS a fraction, after all. But to say that NPR "really doesn't need your money" is a gross factual error.
I, for one, would like to see you post a correction.