Not mad, disappointed. It just seems embarrassing for them that they're struggling so hard to live up to their value of being "listener supported" that they have to accept sponsors like this to survive.
It sounds to me like you are disappointed that the liberal bubble isn’t as thick as it could be. That even accepting supporting money from the bad people is compromising.
It seems that you are implying that the sponsors of NPR get a say in their programming and reporting? Seems like that is the thing I would be upset about, not that the “wrong people” are supplying the money.
It’s NPR, and clearly an atheistic listener there. Are you surprised at this complaint? Christianity is largely anti-science and works against many of the purposes NPR espouses like climate, public health, science and tech, major topics all over NPR. It’s not a stretch to accept this complaint as valid to many left wing rationalist NPR listeners.