If conservatives want to defund NPR, it's likely not going to work that well. The lion's share of NPR's funding comes from local public radio station with very little coming in the way of direct Feds-to-NPR money. The best you could do is to defund the Corporation for Public Broadcasting, which provides 10% of public radio budgets.
The problem with zeroing out CPB is that you go after PBS as well as NPR. When they tried that back in the Newt era, the backlash over getting rid of Barney and Big Bird was more than expected.
Even if you managed to do that, you'd merely put a 10% hit into local budgets and a 5% hit into NPR's budget, if the 50% or so coming from stations gets pro-rated into NPR's bottom line. That would likely be made up from more help at the state government level and more donations.
Since part of the worry of conservatives is NPR getting help from George Soros and other denizens of the left, a defunded NPR is likely to get more ideological rather than less, assuming that the donors will give it more of a leftward list than the government cash does.
It's an issue that gets the base juiced, but it's something of a fool's errand in the bigger picture, making the right look petty rather than principled. It won't save much money and will actually increase NPR's leftward lean.